5. FRESH-WATER DIATOMS FROM ICELAND BY ERNST 0STRUP WITH 5 PLATES 1918 The Botany of Iceland. Vol. II. n n 1 lie manuscript was completed at the death of the author, April the 16th 1917; it was written in Danish, and the translation into English has been effected later. THE EDITORS. PREFACE THE material on which the present paper is based, was like the salt-water material, entrusted to me for examination by the Botanical Museum, Copenhagen University. It comprises in all 572 samples, and has been collected by: cand. mag. J. Boye Petersen (B. P.), cand. O. Davidsson (O. D. f ), Professor A. Feddersen (A. F. f), Professor Chr. Granlund (Grld.f), Professor Th. Holm (Ho.), cand. mag. Hjalmar Jensen (Hj. Js.), Dr. phil. Helgi Jonsson (H. Js.), Professor Dr. phil. L. Kolderup Rosenvinge (K. Rsv.), Dr. phil. C. H. Ostenfeld (C. H. O.), Professor Dr. phil. K. Rerdam (Rd.), Professor Jap. Steenstrup (Stp. f), Skoleforstander St. Stefansson (St.), Adjunkt B. Sasmundsson (B. S.), Professor Dr. phil. Th. Thoroddsen (Th.), Dr. phil. C. Wesenberg-Lund (W. L.), Professor Dr. phil. E. Warming*). Special thanks are due to Prof. Dr. phil. Th. Thoroddsen for his valuable assistance in revising and correcting the names of the Icelandic localities. As to the indication of the parts of the country, these have been copied from the labels, where the localities as a rule have been plainly marked. In this way the samples are apportioned as follows: South, given in the text as S 127 samples South-West S.W 148 North- West - N.W 12 North N 87 East E.' 191 No locality s. 1. (sine loco) 7 Total... 572 samples In case a form is found in no more than 3 samples, these are noted and the name of the collector is added. *) The letters in brackets, affixed to the names of the collectors indicate the abbreviations of their names as used in the text; f signifies that the person is by now deceased. 4 ERNST 0STRUP: FRESH-WATER DIATOMS FROM ICELAND Wherever an apparent discrepancy may be noted, between the number of samples given and those of the list above (f. inst. in the case of Meridion circulare, 15 samples are recorded from N.W., while the list only gives 12 samples from this division) the reason is, that the fresh-water forms occurring at the Icelandic coast are included in the present treatise. The names Europe, Africa, Asia, America, Australia, Greenland, Jan Mayen, Beeren Island, Spitzbergen, Franz Joseph Land are re- spectively abbreviated: Eur., Af., As., Am., Aust., Grl., J. M., B. E., Spb., Fz. J. When the list shows a name marked with an *, it indicates, that the form has been found previously in Iceland. The number of such forms amounts in all to 131. PENNAT.E Euraphideae diraphideae Caloneis Cl. 1894. Cl. Syn. I, 46. Caloneis alpestris (Grun.) Cl. Cl. Syn. I, 53. V. H. Syn., Tab. XII, fig. 30 (Navicula alp.). 5 samples (S. 2, S.W. 1, E. 2). Area: Eur., Aust. *Caloneis amphisbaena (Bory) Cl. Cl. Syn. I, 58. V. H.Trt., Tab. V, fig. 203 (Nav. amph.). 10 samples (S. 3, S.W. 7). Hot spring: 1. Area : Eur., Af., As., Am., Grl., B. E. Caloneis bacillaris (Greg.) Cl. Cl. Syn. I, 50. V. H. Syn., Tab. XII, fig. 27 (Nav. bac. thermalis). Hvita (S.) A. F., HornarfjorSrfljot (E.), St. Area: Eur., As., Am. Caloneis? bodonensis (Pant.) var. Heribaudi M. Per. Cl. Syn. I, 53. Herib. Auv., Tab. IV, fig. 8 (Nav. Herib.). Seydisfjord (E.), H. Js. Area : Eur. Caloneis Clevei (Lgst.) Cl. Cl. Syn. 1, 51. Lgst. Spb., Tab. I, fig. 10 (Nav. Clevei). Hofsfjall (N.), O. D.. Area: Eur., As., Grl., J. M., Spb., Fz. J. Caloneis fasciata (Lgst.) Cl. Cl. Syn. I, 50. V. H. Syn., Tab. XII, fig. 34 (Nav. fasc.). 46 samples (S. 13, S.W. 19, N. 7, E. 5, s. 1. 2). Hot springs: 2. Area: Ubiquist., Grl., J. M., Spb., Fz. J. Caloneis Fedderseni sp. nov., Tab. nost. I, fig. 1. Long: 42 /<, lat: 8 //, str. 16 in 10^, subtiliter punctatis. Valva fere lineari, apicibus rotundatis. Raphe area hyalina distincta, media in parte valvae paululum dilatata, cincta. Striis <) ERNST 0STIU I' medianis aliquantulum spatiatis, apices versus densioribus, per totain valvam radiantibus. Reykholtshver (S.) A. F. Caloneis islandica sp. nov., Tab. nost. I, fig. 2. Long: 64//, lat: 10 it, str. 20 in 10 //. Valva lineari, apicibus rotundatis. Rapbe area byalina distincta, media in parte valvse in areolam rotundatam, in qua lunulse du;e adsunt, dilatata, cincta. Laugarvatn E.) B. P. This form is probably related to, but hardly identical with Gal. alpestris (Grun.) Cl. Caloneis Jonssoni sp. nov., Tab. nost. I, fig. 3. Long: 35 /*, lat: 5,5 /<, str. 16 in 10 //. Valva lineari, in medio leniter contracta, apicibus rotundatis. Haphe area hyalina lata, media in parte valva in fasciam dilatata. cincta. Striis parallelis. Nordfjordr (E.) H. .Is. Caloneis Ladogenis Cl. Cl. Syn. I, 62. Cl. Finl., Tab. II, fig. 3. 4 samples (S. 1, S.W. 1, N. 1. E. 1). Area: Eur. Caloneis obtusa (W. Sm.) Cl. Cl. Syn. I, 54. Donk. Br. Dial., Tab. Ill, fig. 12 (Navicula Hebes). 4 samples (all E.). Area: Eur. Caloneis procera sp. nov., Tab. nost. I, fig. 4. Long: 104 //, lat: 12 //, str. c. 25 in 10 //. Valva lineari in medio leniter inflata. Rapbe area hyalina, media in parte valva paululum patescente, cincta. Striis parallelis. Vallanes (E.) B. P. This form has some similarity with Cal. Liber (W. Sm.) Cl., but has not the terminal nodi so characteristic of this latter, and it was found in a sample entirely containing fresh-water forms. The irregularly dis- tributed ridges, illustrated in the figure, are possiby the outcome of a diseased condition. *Caloneis Silicula (Ehr.) Cl. Cl. Syn. I, 51. V. H. Trt., Tab. V, li-. 207 (Navicula limosa). 151 samples (S. 35, S.W. 39, N.W. 7, N. 22, E. 40, s. 1. 2. Hot springs: 10. Area: Ubiquist, Grl., B. E. *Var. nlpina Cl. Cl. 1. c. V. H. Syn., Tab. XII, fig. 21 (Xav. Silicula). 24 samples (S. 6, S.W. 10, N. 3, E. 5). Hot springs: 5. Area: Eur., Grl., J. M., Spb., Fz. J. FRESH-WATER DIATOMS FROM ICELAND i Var. biconstricta 0st. 0st. D. D. 15, Tab. I, fig. 6. 7 / 1 7 Egilstadir (E.) B. P. Area : Eur. *Var. inflata Grun. Cl. Syn. I, 51. V. H. Syn., Tab. XII, iig. 20 (Nav. limosa subinflata). 5 samples (S. 3, S.W. 2). Hot springs: 2. Area: Eur. Var. siibventricosa Grun. Cl. 1. c. 52. Cl. & Gr. A. D., Tab. 1, fig. 19 (Nav. subv.). Thingvellir (S.W.) E. W. & Ho. Area: Kara. Var. ventricosa (Ehr.) Donk. Cl. 1. c. V. H. Trt., Tab. V, fig. 209 (Nav. vent.). Ketilstadir (S.W.) H. Js. Area: Eur., As., Grl., Fz. J. Neidium Pfitzer 1871. Cl. Syn. I, 67. Neidium affine Ehr. var. amphirhynchus Ehr. Cl. Syn. I, 68. V. H. Trt., Tab. V, fig. 214 (Nav. Iridis amph.). 47 samples (S. 8, S.W. 14, N. 4, E. 20, s. 1. 1). Hot springs: 5. Area: Eur., Aust., Grl., B. E., Spb. Var. hngiceps Greg. Cl. I.e. Greg. Mic. J. IV, Tab. I, fig. 27. Eirtar (E.) H. Js. Area : Eur., Grl. Var. undnlata Grun. Cl. 1. c. V. H. Trt., Tab. V, fig. 216 (Nav. Irid. und.). Sandbrekka (E.) H. Js., Vallanes E.) H. Js. Area: Eur. Neidium bisulcatum (Lagst.) Cl. Cl. Syn. I, 68. Lgst. Spb., Tab. I, fig. 8 (Nav. bisulc.). 41 samples (S. 6, S.W. 10, N. 4, E. 20, s. 1. 1). Hot spring: 1. Area: Eur., Af., As., Am., Grl., J. M., B. E., Spb., Fz. J. Neidium dilatatum (Ehr.) Cl. Cl. Syn. I, 70. A. S. All., Tab. XLIX, fig. 6. 7 samples (S. 2, S.W. 3, E. 2). Area: Eur. Neidium dubium (Ehr.) Cl. Cl. Syn. I, 70. 10 samples (S. 4, N. 5, E. 1). Hot springs: 2. Area: Eur., As., Am., Aust. The above samples, corresponding with the figures in A. S. Atl., Tab. XLIX, figs. 8, 11, 14 and 24, all come within the group of Neidium dubium. ERNST 0STRUP Neidium fasciatum 0st. 0st. D. D. 21, Tab. 1, fig. 14. Gautavik (E.) H. Js.. Vallanes (E.) H. Js. Area: Eur. Neidium Hitchcockii (Ehr.) Cl. Cl. Syn. 1, 69. A. S. Atl., Tab. XLIX, fig. 35 & 36 (Nav. Hitch.). Vallanes (E.) H. Js. Area : Eur., As., Am., Aust. Neidium incurvum (Greg.) 0st. Tab. nost. I, fig. 5, cnfr. Greg. Mic. .1 IV, 8, Tab. I, fig. 26 (Nav. inc.). Long: 45/<, lat: 10 & 11 ju. Valva elongata, in medio leniter incurvata, apicibus capitatis. Xodulis terminalibus summis in apicibus positis. Raphe area hyalina angustissima, media in parte valvae in areolam parvam dilatata, cincta. Structuram ullam valvse perspicere non potui. Grimsa (E.) B. P. Area: Eur. I consider this form identical with Gregory's Navicula incurva. The u fragliche" form delineated in A. S. Atl., Tab. XLIX, fig. 13, from Loch Davin, Scotl.. must surely be referred to this. *Neidium Iridis (Ehr.) Cl. Cl. Syn. I, 69. V. H. Trt., Tab. V, fig. 212 (Nav. Ir.). 5 samples (S.W. 3, E. 2). Ubiquist. Grl., Fz. J. Neidium islandicum sp. nov., Tab. nost. I, fig. 6. Long: 30 //, lat: 7 /<. Valva elliptice-lanceolata, apicibus rotundatis. Raphe area hyalina angusta, mediam partem valvse versus patescente ibique in fasciam latam dilatata, cincta. Lineis inframarginalibus distinctis. Striis segre perspiciendis. Brunavikurstrand (E.) H. Js. Neidium lineare sp. nov., Tab. nost. I, fig. 7. Long: 41 //, lat: 6,4 //. Valva lineari, apicibus rotundatis. Raphe area hyalina angusta, media in parte valvse in fasciam satis latam dilatala. Lineis infra- marginalibus distinctis. Vallanes (E.) B. P. This small form is possibly related to, but not identical with Neid. bisulcatum. Neidium panduriforme sp. nov., Tab. nost. I, fig. 8. Long: 22 /*, lat: 8& 9,5 //. Valva panduriformi, linea inframarginali instructa. Raphe media FRESH-WATER DIATOMS FROM ICELAND 9 in parte valvae modo conspicua. Striae delicatissimae, et apicales et transapicales, adsunt. Reykjarfjord (N). In a hot spring. I am not sure as to the classification of this small form. Considering the marginal line, I am inclined to place it under Neidium. Neidium productum (W. Sm.) Cl. Cl. Syn. I, 69. V. H.Trt., Tab. V, fig. 218. (Nav. Irid. prod.). Stadastadur (S.W.), H. Js., Sydri Gardar (S.W.) H. Js., Vatnsdalsa (N.) St. Area: Eur., As., Am. Diploneis Ehr. 1840. Cl. Syn. I, 76. Dlploneis Boldtiana Cl. Cl. Syn. I, 92. Cl. Finl., Tab. II, fig. 12. 4 samples (S. 1, S.W. 2, N.W. 1). Area: Eur. Var. robusta A. Cl. A. Cl. Finl. 12, Tab. I, fig. 8. Spoastadir (S.) A. F. Area: Eur. *Diploneis elliptica (Ktz.) Cl. Cl. Syn. I, 92. V. H. Trt., Tab. IV, fig. 156, 1st fig. (Navicula ell.). 140 samples (S. 29, S. W. 35, N.W.I, N. 26, E. 42. s. 1. 7). Hot springs: 18. Area : Ubiquist, Grl., Fz. J. 'Diploneis ovalis (Hilse) Cl. Cl. Syn. I, 92. V. H. Trt., Tab. IV, fig. 156, 2d fig. (Nav. ell. ovalis). 49 samples (S. 7, S.W. 12, N.W. 1, N. 8, E. 20, s. 1. 1). Hot spring: 1. Area: Eur.. Am., Aust, Grl., J. M., B. E. Var. oblongella NaBgeli. Cl. Syn. I, 93. V. H. Trt., Tab. IV, fig. 157 (Nav. ell. oblong.). 86 samples (S. 15, S.W. 16, N.W. 1, N. 5, E. 45, s. 1. 4). Hot springs: 5. Area: Eur., Af., As., Am. Forma subinflata, Tab. nost. I, fig. 9. Long: 38 //, lat: 9 & 10 /*, str. 14 in 10 //, apices versus densi- oribus. Valva lineari, media in parte leniter inflata, ceterum Dipl. ov. obi. simili. Reykjavik (S.W.) C. H. O. Doubtless it is this form about which Hustedt (Sudet., 67) under Dipl. ov. obi. adds: "Zuweilen sind die Exemplare in der Mitte leicht transapikal erweitert." Forma pumila Grim. Cl. Syn. I, 92. Grun. Oest. Ung., Tab. XXX, fig. 61 (Nav. ov. pum.). Hrossholt (S.W.) A. F. In a hot spring. Area: Eur., As. 10 ERNST 0STRUP Diploneis Puella uSdium.?) Cl. Cl. Syn. I, 92. V. H. Trt., Tab. IV. fig. 15cS (Xav. ell. minima). Myvntn N. Hd.. Akureyri X. B. P. Area: Eur.. Af.. Sph. Diploneis subovalis Cl. Cl. Syn. I, 9(5, Tab. I, fig. 27, Tab. nost. 1. li. 10. Stori Kroppur (S.W.) B. P. Area: NV\v Zealand. I have given a delineation of the form found by me, as it differs somewhat from Cleve's figure. About its identity with Dipl. subov. I have no doubt whatever. Naviculae orthostichae Cl. Cl. Syn. I, 107. Mavicula cuspidata Ktz. Cl. Syn. I, 109. V. H. Trt., Tab. IV, fig. I'm. 5 samples (S. 1, SW. 1. X. 1. K. 2 Area : Ubiquist. B. E. Var. ambigua Ehr. Cl. Syn. I, 110. V. H. Trt., Tab. IV. fig. 192 (Xav. amb.). 9 samples (S. 3, S.W. 2, X. 2, E. 2). Hot spring: 1. Area: Ubiquist, Grl. Var. Heribamli M. Per. Cl. Syn. I, 110. Herih. Auv., Tab. IV, fig. 1(5. Reykjavik (S.W. B. P. Area: Eur. fossil.. Gyrosigma Hassall 1845. Cl. Syn. I, 112. Gyposigma acuminatum (Ktz.) Cl. Cl. Syn. I, 114. V. H.Trt., Tab VII, fig. 274 (Pleuros. acum.). 4 samples (S.W. 2. XAV. 1, N. 1). Area: Eur. Af., As. 'Gyrosigma attenuatum (Ktz.) Cl. Cl. Syn. I, 11."). V. H.Trt., Tab. VII, fig. 271 (Pleuros. alien.). Reykjavik (S.W.) C. H. O., Grimsey (N.) O. D. Area: Eur., Af., As., Am. Frustulia Ag. 1824. Cl. Syn. I, 121. Frustulia islandica sp. nov., Tab. nost. I, fig. 11. Long: 4(5 //, lat: 9 //. Valva lanceolata, apicibus leniter attenuatis. Raphe intra costas siliceas duas sita. Nodulis terminalibus ab apicibus remotis. Striis subtilissimis el, quoad perspicere polui, radiantibus, media in parte valvse deficientibus ibique fasciam latam relinquentibus. Sselsundslaekur (S.) A. F. FRESH-WATER DIATOMS FROM ICELAND 11 Frustulia rhomboides (Ehr.) Cl. var. saxonica Rabh. Cl. Syn. I, 123. V. H. Trt., Tab. V, fig. 250 (Van Heurckia rhomb, crassin.). 24 samples (S. 4. SAY. 11, N. 2, E. 7). Hot springs: 2. Area: Ubiquist, Grl., B. E., Spb. Var. leptocephala 0st. 0st. 0stg. Fersk. 257, Tab. I, fig. 1. 7 samples (S. 2, SAY. 3, N. 2). Hot spring: 1. Area: Grl. Frustulia vulgaris Thw. Cl. Syn. I, 122. V. H.Trt, Tab. V, fig. 252 (Van Heur. vulg.). 116 samples (S. 28, S. W. 32. N.W. 4, N. 12, E. 39, s. I. 1;. Hot springs: 10. Area: Ubiquist. Grl. Amphipleura Ktz. 1844. Cl. Syn. I, 125. Amphipleura pellucida Ktz. Cl. Syn. I, 126. V. H. Trt, Tab. V, fig. 253. 9 samples (S. 3, SAY. 2, E. 4). Area : Eur., As. Naviculae mesolejae Cl. 1894. Cl. Syn. I, 127. NaviculabacilliformisGrun. Cl.Syn. I, 131. V. H.Trt., Tab. XXVII, fig. 774. 17 samples (S. 3, SAY. 3, N.I, E. 10). Area: Eur., As.. Am., Aust. Navicula Heufleriana Grim. Cl. Syn. I, 130. V. H. Syn., Tab. IV, fig. 1 a (Stauroneis Heufleri). 5 samples (S. 3, N. 1, E. 1). Area: Eur., Grl., Fz. J. Navicula mutica Ktz. forma Cohni Hilse. Cl. Syn. I, 129. V. H. Trt., Tab. IV, fig. 167 (Nav. mut.). 20 samples (S. 6, SAY. 6, NAV. 2, N. 4, E.I). Hot springs: 3. Area: Ubiquist, Grl., J. M., Spb., Fz. J. Forma Goppertiana Bleiscb. Cl. Syn. I, 129. V. H. Trt., Tab. IV, fig. 168. Vallanes (E.) H. Js. Area: Eur., As., Am., Grl. Navicula nivalis Ehr. Cl. Syn. 1, 130. V. H. Trt., Tab. IV, fig. 178 (Nav. mut. quinquenodis). 5 samples, all N. Hot springs : 4. Area: Eur!, Af., Aust., Grl., Fz. J. 12 ERNST OSTRUP *Navicula Pupula Ktz. Cl. Syn. I, 131. V. H. Trt., Tab. V, fig. 226, 1st fig. 29 samples (S. 5, S.W. 9, N. 6, E. 9). Hot springs: 3. Area: Ubiquist, Grl. Navicula Rotaana Rabh. Cl. Syn. I, 128. V. H. Syn., Tab. XIV, figs. 1719. 5 samples (S.W. 2, N. 1, E. 2). Area: Eur., Aust., Grl., J. M., B. E., Spb., Fz. J. Var. oblongella Grim. Cl. 1. c. V. H. Syn. 1. c., fig. 21. 8 samples (SAY. 3, N. 2, E. 2, S.L.I). Hot spring: 1. Navicula Seminulum Grun. Cl. Syn. I, 128. V. H. Trt., Tab. V, fig. 228. Eystri Ranga (S.) A. F., Vik V S.) H. Js., Thingvellir (SAY.; E.\V. &Ho. Area: Eur., As., Am., Grl., B. E., Spb., Fz. J. Var. fragilaroides Grun. Cl. Syn. 1. c. V. H. Syn., Tab. XIV, fig. 10. Berufjordur (E.) H. Js. Area: Eur. Naviculae entolejae Cl. 1894. Cl. Syn. I, 131. *Navicula contenta Grun. var. biceps Arnott. Cl. Syn. I, 132. V. H. Trt., Tab. V, fig. 240. 17 samples (S. 6, S.W. 5, N. 2, E. 4). Hot spring: 1. Area: Eur., As., Grl. Naviculae bacillares Cl. 1894. Cl. Syn. I, 136. *Navicula Bacillum Khr. Cl. Syn. I, 137. V. H. Trt., Tab. V, fig. 222. 5 samples (S. 2, S.W. 1, N. 1, E. 1). Area: Eur., As., Am., Aust. Var. densestriata var. nov., Tab. nost. I, fig. 12. Long: 37 //, lat: 8 //. Valva lineari, apicibus rotundatis. Raphe area hyalina angustis- sima, media in parte valvse in areolam rotundatam dilatata, cincta. Striis subtilissimis, radiantibus, in medio ali([uantulum spatiatis. Ingjaldsholl (S.W.) H. Js. Var. Icjnda Greg. Cl. Syn. I, 137, Tab. V, fig. 14. Skeidararsanfiur (S.) St. Area: Eur., Am. Var. minor H. V. H. Cl. Syn. 1. c. V. H. Trt., Tab. V, fig. 223. Adalvik (N.W.) C. H. O. Area: Eur., Aust. FRESH-WATER DIATOMS FROM ICELAND 13 Navicula Pseudobacillum Grim. Cl. Syn. I, 137. V. H. Trt., Tab. V, fig. 224. 5 samples (S. 2, SAY. 2, E. 1). Area: Eur., Af, As., Aust., Grl. Var. lanceolata 0st. 0st. D. D. 40, Tab. 1, fig. 29. Myvatn (N.) B. P. Area: Eur. Naviculae decipientes Grun. 1880. Cl. Syn. I, 138. Navicula crucicula W. Sm. Cl. Syn. I, 139. V. H. Trt., Tab. IV, fig. 138. 7 samples (S.W. 5, N.W. 1, E. 1). Area: Eur., Af., As., Aust., Grl. Var. capitata 0st. 0st. D. D. 42, Tab. I, fig. 30. SkeiAararsandur (S.) St. Area: Eur. Navicula Integra W. Sm. Cl. Syn. I, 141. V. H.Trt., Tab. IV, fig. 174. Skeidararsandur (S.) St., Reykjavik (S.W.) B. P. Area : Eur. Navicula protracta Grun. Cl. Syn. I, 140. V. H. Trt., Tab. IV, fig. 173 (Nav. crucic. protr.). 9 samples (S. 5, S.W. 3, E. 1). Area: Eur., Af. *Navicula Semen Ehr. Cl. Syn. 1, 138. Grun. Fz. J., Tab. 1, fig. 34. 49 samples (S. 4, S,W. (5, N.W. 2, N. 8, E. 29). Hot springs: 2. Area: Eur., Am., Fz. J. Navicula subtilissima Cl. Cl. Syn. I, 141. Cl. Finl., Tab. II, fig. 15. Reykjavik (S,W.) C. H. O. Area : Eur., Spb. Naviculae microstigmaticae Cl. 1894. Cl. Syn. I, 141. Stauroneis Ehr. 1843. Cl. Syn. I, 144151. *Stauroneis acuta W. Sm. Cl. Syn. I, 150. V. H.Trt., Tab. I, fig. 51. Mafahlid (S.W.) H. Js., Hofsa (N.) O. D. Area: Eur., As., Am., Aust., Grl., Fz. J. *Stauroneis anceps Ehr. Cl. Syn. I, 147. V. H. Trt., Tab. I, fig. 55. 66 samples (S. 13, S.W. 8, N. 9, E. 36). Hot spring: 1. Area: Ubiquist, Grl., J. M., B. E., Spb., Fz. J. Under Staur. anc. I also include var. amphicephala Ktz. V. H. Trt., Tab. I, fig. 57, as this can scarcely be distinguished from the type. Var. birostris Ehr. Cl. Syn. 1. c. Cl. Grl. & Argent., Tab. XVI, fig. 5. Egilstadir (E.) B. P. Area: Eur., Am. 14 ERNST 0STRUP Var. elliptica var. nov., Tab. nost. I, fig. 13. Long: 26//, lat: 7,2 //. Valva elliptica, apices subcapitatos versus attenuata. Raphe area hvalina, mediani partem valvae versus patescente, cincta. Stauro satis lato. Striis subtilissimis, radiantibus. Hreidarsstaftir (E.) B. P. *Var. (jracilis Ehr. Cl. Syn. 1, 147. A. S. All., Tab. CCXLII, fig. 7 12. Gljufurholtsa (S.) B. P.. Stori Kroppur S.W.) B. P.. Myvatn X.) Rd. Area: Eur., Am. Var. hyalina Br. & Per. Cl. Syn. 1. c. Herib. Auv., Tab. Ill, fig. 19. 4 samples, all E. Area: Eur., Aust. *Var. linearis Ehr. Cl. Syn. 1. c. V. H. Trt., Tab. 1, fig. 56. Isafjord (N.W.) B. P., Njardvik (E.) H.Js., Sasvarendi (E.) H. .Is. Area: Eur., Aust. Var. siberica Grun. Cl. Syn. 1. c. Cl. & Grim. A. D., Tab. Ill, lig. !>.">. 9 samples (S. 2, S.W. 4, E. 3). Stauroneis bifissa sp. nov., Tab. nost., fig. 14. Long: 34 //. lat: 8 //. Valva lanceolata, apicibus productis. Raphe area hyalina, mediam partem valva> versus patescente, cincta. Slauro satis lato, utrisque in lateribus linea singula instructa. Striis inconspicuis. Glammarstaclavatn (SAY/, B. P.. Yallanes (E.) B. P. Stauroneis elegantula sp. nov., Tab. nost. I, fig. 15. Long: 28 //, lat: 5,5 n. Valva elliptica, apices capitatos versus attenuata. Raphe area hyalina angusta, mediam partem valvae versus patescente, cincla. Stauro latissimo. Striis inconspicuis. Beykholt (S.W.) H.Js. Stauroneis Javanica Grun. Cl. Syn. I, 150. Grun. Nov., Tab. I, lii; 14. 0st. 0stg. Ferskv., Tab. I, fig. 4. 4 samples -SAY. 2, E. 2). Area: Eur., As., Am., Aust., Grl. In a sample from a valley near Isafjord N.W.) B. P., I have found a Staronc'is javanica of the following dimensions: length 78 //, width 21 //, consequently shorter and comparatively broader than the type. Stauroneis Legumen Ehr. Cl. Syn. I, 149. V. H.Trt., Tab. I, iig. 59. 5 sampk-s (S. 1, SW. 1. N.W. 2, N. 3, E. 1). Area: Eur.. Af, As.. Am., Grl. FRESH-WATER DIATOMS FROM ICELAND 15 Stauroneis obtusa Lgst. Cl. Syn. I, 149. Lgst. Spb., Tab. I, fig. 11. Ketilsstadir (S.W.), H. Js. Area: J. M., Spb., Fr. J. Stauroneis parvula Grim. Var. prodncta Grim. CI. Syn. I, 149. V. H. Syn., Tab. IV, fig. 12. 31 samples (S. 2, S.W. 14, N.W. 3, N. 3, E. 9). Area: Eur., Grl. Var. capitata var. nov., Tab. nost. I, fig. 16. Long: 4(3 //, lat; 10 //. Valva elliptica, apicibus capilatis, diaphragmate distincto instruc- tis. Raphe area hyalina distincta cincta. Stauro satis angusto. Striis subtilissimis, radiantibus. Reykjavik (SAY.!, Stp. This form is nearest to Staur. parv. prod, tor in a subcapitata in my D. D. P. 47, Tab. II, fig. 34, but to me it seems nevertheless differing suf- ficiently for placing it as a special variety. Stauroneis perexilis sp. nov., Tab. nost. I, fig. 17. Long: 20 , lat: 4,5 /<. Valva lanceolata, apicibus diaphragmate instructis. Raphe area hyalina angusta, mediam partem valvse versus patescenti, cincta. Structuram ullam valva? perspicere non potni. Reykjavik (S.W.), H. Js. *Stauroneis Phonicenteron Ehr. Cl. Syn. 1, 148. V. H. Trt., Tab. I, fig. 50. 65 samples (S. 6, S.W. 20, N.W. 3, N. 10, E. 25, s. 1. 1). Hot spring: 1. Area: Ubiquist, Grl. Var. amphilepta Ehr. Cl. Syn. I, 149. Herib. Auv., Tab. Ill, fig. 18. 30 samples (S. 6, S.'W. 7, N.W. 1, N. 2, E. 14). Area: Eur., Afr., Aust., Grl., B. E. Stauroneis Smith! Grun. Cl. Syn. I, 150. V. H. Trt, Tab. I, fig. 58. Skeidararsandur (S.) St., Vallanes (E., two samples), H. Js. Area: Eur., As., Am. S. Stefanssoni sp. nov., Tab. nost. II, fig. 18. Long: 46 ,, lat: 8 //, str. 20 in 10 //. Valva lanceolata, margine undulato, in medio leniter inciso. Apicibus apiculatis, diaphragmate distinclo instructis. Raphe area hyalina angusta cincta. Stauro bifisso. Striis radiantibus. Skei5ararsandur (S.) St. This pretty and characteristic form probably belongs to the group of St. Smithi. It has the median constriction in common with St. Smithi var. incisa: Pant, in Pant. Bel. S., 27, Tab. II, fig. 45, but differs otherwise to such extent, that I do not think it can be classed with this form; nor can it be identical with Schizostauron Karsteni O. M. in Ch. Nyassa, 88, Tab. II, figs. 17 18. It undoubtedly deserves a place as a distinct species. 16 ERNST 0STRUP Cymbella Ag. 1830. GI. Syn. I, 156. *Cymbella aequalis W. Sm. Cl. Syn. I, 170. V. H. Trt., Tab. I, fig. 26 (C. suhsequ.) & fig. 27 (C. obtusa). 12 samples (S. 8, S.W. 18. NAY. 1, X. 2, E. 13). Hot spring: 1. Area: Eur.. Afr., As., Am., Grl. Cymbella affinis Ktz. Cl. Syn. I, 171. V. H. Trt., Tab. I, fig. 31. 7 samples (S. 1, SAY. 2, E. 4). Area: Ubiquist, Grl., Spb. *Cymbella amphicephala Naegeli. Cl. Syn. I, 164. V. H.Trt, Tab. I, fig. 25. 15 samples (S. 3, S.W. 1, E. 11). Area: Ubiquist. Grl., Spb., Fr. J. Cymbella angustata W.Sm. Cl. Syn. 1, 161. Lgst. Spb.Tab. II, fig. 10. 7 samples (S.W. 3, E. 4). Area: Eur., Grl., Spb. *Cymbella aspera Ehr. Cl. Syn. I, 175. V. H. Trt. I, fig. 35 (C. ga- stroides). 44 samples (S. 2, S.W. 18, NW. 4, N. 3, E. 22). Hot spring: 1. Area: Ubiquist, Fr. J. Var. dubravkensis Grun. Cl. Syn. 1. c. Grun. Foss. Oestr. Tab. XXIX, fig. 30. Mvvatn (N.), Rd. Area: Eur. *Cymbella Cesatii Rabh. Cl. Syn. I, 160. V. H. Trt., Tab. Ill, fig. 143 (Navicula Ces.). Reykjavik (S.W;, H. Js. Area: Eur., Am., Grl., Spb. *Cymbella Cistula Hempr. Cl.Syn. I, 173. V. H. Trt., Tab. I, fig. 40. 100 samples (S. 38, S.W. 27, N. 5, E. 22, s. 1. 2). Hot spring: 1. Area: Ubiquist, Grl., Spb. Var. arctica Lgst. Cl. Syn. 1. c. Lgst. Spb., Tab. II, fig. 21 (Cymb. variab. arct). Modruvellir (S.W.), B. P. Area: Eur., As., B. E., Spb. Var. Caldogastensis Prud. Prud. Lacs du Jura IV. P. 22, Tab. I, fig. 1. Tab. nost. II, iig. 19. Long: 126 /i, lat: 23 //. Str. 8 in 10 /*, distincte punclatis. Vulva cymbiformi, margine ventrali in medio leniter inilata. Ruphe area hyalina satis lata, media in parte valvic in aream rotun- datam dilatala, cine-la. Utraque in parte areae centralis puncta soli- FRESH-WATER DIATOMS FROM ICELAND 17 taria adsunt, et quidem 5 in parte dorsali, 7 in parte ventrali. No- dulis terminalibus ab apicibus remotis. Laugarvatn (S.), A. F. Area: Eur. This Cymbella is decidedly Prudent's above mentioned variant of C. Cist, but hardly identical with Cymb. Nordenskjoldi O. M. (O. M. Patag. P. 25, Tab. I, fig. 18) which has a similar double set of puncta. Var. maculata Ktz. Cl. Syn. 1, 173. V. H. Trt., Tab. I, fig. 41. Gljufurholtsa (S.) B. P., Saelulaskr (S.W.) A. F., Stadarhraun (S.W.) A. F. Area: Eur.. Am., Grl., Spb., Fz. J. Cymbella cuspidata Ktz. Cl. Syn. I, 160. V. H. Trt., Tab. I, fig. 23. 23 samples (S. 5. S.W. 8, N. 3, E. 7). Area: Ubiquist, Grl. *Cymbella cymbiformis (Ag.) Ktz. Cl. Syn. I, 172. V. H. Trt., Tab. I, fig. 38. 20 samples (S. 2, S.W. 9, N.I, E. 8). Hot springs: 2. Area: Ubiquist. Cymbella dubia sp. nov.. Tab. nost. II, fig. 20. Long: 43 /<, lat: 6,4 /<. Str. 12,5 in 10 /<. Valva linear!, apicibus rotundatis. Raphe obliqua, area hyalina, media in parte valvse unilateraliter in areolam rotundatam dilatata, cincta. Striis per totam valvam radiantibus. Mjoanes (E.) B. P. By reason of the oblique raphe, the stria? radiating throughout and the unilateral central area, I have considered it proper placing this form as a Cymbella. Cymbella Ehrenbergi Ktz. Cl. Syn. I, 165. V. H. Trt., Tab. I, fig. 22 (greatest fig.). 23 samples (S. 8, S.W. 6, N. 3, E. 6). Var. delecta A.S. Cl.Syn. 1. c. A.S. Atl., Tab. IX, fig. 17 (Cymb. del.). Myvatn (N.), B. P. Area: Eur., Am., Aust., Grl. Cymbella gracilis Rabh. Cl. Syn. I, 169. V. H. Trt., Tab. XXVIII, fig. 791 bis b (Encyon. grac.) and 791 bis c (Enc. lunatum). 79 samples (S. 4, S.W. 26, NW. 3, N. 14, E. 31, s. I. IX Hot springs: 2. Area: Ubiquist, Grl. Cymbella helvetica Ktz. Cl. Syn. I, 174. V. H. Trt., Tab. I, fig. 43. 57 samples (S. 11, SW. 22, N. 6, E. 17, s. 1. 1). Hot springs: 2. Area: Eur., Grl. *Cymbella heteropleura Ehr. var. minor Cl. Cl. Syn. I, 167. A. S. Atl., Tab. IX, fig. 52. 41 samples (S. 4, S.W. 9, N.W. 2. N. 8, E. 17, s. I. 1). Hot springs: 2. Area: Eur., As., Grl., Spb. The Botany of Iceland. Vol. II. 18 ERNST 0STRUP Cymbella incerta Grim. var. nnincnlacea Grim. Cl. Syn. I, 170. Cl. Grl. & Arg., Tab. XVI, fig. 11. 7 samples S.W. 5, E. 2 . Hot spring: 1 Area : Eur., Grl. Cymbella islandica sp. nov., Tab. nost. II, fig. 21. Long: 100 /, lat: 11 //, str. 12 in 10 //, subtiliter punctatis. Valva cymbiformi, margine ventral! fere recta. Apicibus acutis. Raphe area byalina angusta, media in parte vulva- in a ream longi- nam, marginem ventralem versus aliquantum dilatata, cincta. Egilsta.Mr (E.) B. P. Cymbella Jonssoni sp. nov., Tab. nost. II, fig. 22. Long: 5() //, lat: 9 //, str. 10 in 10 , apices versus densioribus, indistincte punctatis. Valva anguste lanceolata. Raphe area byalina, media in parle valvse in aream asymmetricam dilatata, cincta. Striis per totain valvam radiantibus. Owing to the radiating striation and the non-symmetrical central area I assume this form to be a Cymbella. It has probably nothing to do with Cymb. inc. naviculacea. Cymbella lanceolata Ehr. Cl. Syn. I, 174. V. H. Trt., Tab. I. fig. 37. 99 samples (S. 25, S.W. 20, N. 12. E. 40. s. 1. 2). Hot springs: 2 Area: Eur., Af.. As., Am. Var. cormita Ehr. Cl. Syn. 1. c. 0st. D. D., Tab. II, fig. 43. 8 samples ,S.W. 5, E. 3). Area: Eur. Var. ventricosa A. Cl. A. Cl. Finl. P. 19, Tab. I, fig. 17 (C. lane, in- flata). Reykjavik S.W. C. H. 0. Area: Eur. :;: Cymbella lapponica Grun. Cl. Syn. I, 1(>5, Tab. IV, fig. 28. 26 samples S. 5. S.W. 10, N.W.I, N.I. E. 9). Hot spring: 1. Area: Eur. Cymbella linearis sp. nov.. Tab. nost. II, fig. 23. Long: ()7 //, lat: 6,4 //, str. 12 in 10 /*. Valva linear!, apicibus rostratis. Rapbe directa, fissuris termi- nalibus recurvatis. Striis per totam valvam radiantibus, in apicibus deficienlibus, media in parte valvae areolam rotundatam relinquen- tibus, ceterum rapben attingentibus. Sta^ashuW (S.W. H. Js. Tin's form is without doubt a Cymbella; the peculiar course of the raphe at the apices and the striation radiating throughout, seem to point FRESH-WATER DIATOMS FROM ICELAND 19 in this direction. It is hardly identical with Cymb. amphioxys (Ktz. ? Grun.) Cl. (see Le Diatomiste II, 145, Tab. IX, fig. 6j which however it somewhat resembles. Cymbella marginata sp. nov., Tab. nost. II, fig. 24. Long: 46 //, lat: 7 //, str. 20 in 10 /LI. Valva elliptice-lanceolata. Raphe obliqua. Fissuris terminalibus in eandem partem valvas declinantibus. Striis marginalibus, paral- lelis, aream apicalem latam circa raphen relinquentibus. Egilstadir (S.), B. P. Cymbella microcephala Grun. Cl. Syn. I, 160. V. H. Trt., Tab. I, fig. 34. 8 samples (S. 2, S.W. 3, E. 3). Hot spring: 1. Area: Eur., Am., Grl. Cymbella naviculiformis Auersw. Cl. Syn. I, 166. V. H. Trt., Tab. I, fig. 24 (C. cusp, navicl.). 52 samples (S. 6, S.W. 19, N. 10, E. 16, s. 1. 1). Hot springs: 3. Area: Eur., As., Am., Aust., Grl., B. E., Spb. *Cymbella parva W. Sm. Cl. Syn. I, 172. V. H.Trt., Tab. I, fig. 39 (C. cymbif. parva). 200 samples (S. 40, S.W. 56, NW. 1, N. 22, E. 76, s. 1. 5). Hot springs: 9. Area: Eur., Af., As., Am., Grl., B. E., Fz. J. Cymbella prostrata Berk. Cl. Syn. I, 167. V. H. Trt., Tab. I, fig. 44 (Encyon. prost.). Krokur (S.) H.Js. Area: Eur., Af., As., Am. Cymbella recta sp. nov., Tab. nost. II, fig. 25. Long: 105 //, lat: 18 /*, str. 11 in 10 /*, distincte punctatis. Valva lanceolata, apicibus rotundalis, raphe directa, media in parte valvse in aream satis latam dilatata, cincta. Striis parallelis. Thingvellir (S.W.). B. P. Cymbella sinuata Greg. Cl. Syn. I, 170. V. H. Trt., Tab. XXV, fig. 699 (C. abnormis). 10 samples (S.W 6, N. 2, E. 2). Area: Eur., Af., As., Austr., Grl., B. E. Cymbella stauroneiformis Lgst. Cl. Syn. I, 165. Lgst. Spb., Tab. I, fig. 15. Ormasta&ir (E.) B. P. Area: B. E., Spb. Cymbella subconstricta sp. nov., Tab. nost. II, fig. 26. Long: 42 ( , lat: 6 /, str. 16 in 10 ,, subtiliter punclatis. Valva fere lineari, margiue ventrali in medio leniter incurvata. Striis radiantibus, in apicibus deficientibus, media in parte ventrali 2* 20 ERNST 0STRUP valva? abbreviatis, ihique areolam elongatam relinquentibus, ceteruni raphen attingentihus. Reykjavik (S.W.) H.Js. Cymbella turgida Greg. Cl. Syn. I, 168. V. H. Trt., Tab. I, fig. 45 (Encyon. turg.). Borgarnes E.) H. Js. Area: Eur., As., Am., Aust., Grl. : Cymbella ventricosa Ktz. Cl. Syn. 1, 168. V. H. Trt., Tab. I, figs. 46, 47 & 49 (Encyon. caesp. & ventric.). 247 samples (S. 43, S.W. 71, N.W. 3, N. 35, E. 92, s. I. 3). Hot springs: 5 Area: Ubiquist, Grl., B. E., Spb., Fz. J. Gomphonema Ag. 1824. Cl. Syn. I, 178. *Gomphonema acuminatum Ehr. Cl. Syn. I, 184. V. H. Trt., Tab. VIII, fig. 299. 63 samples (S. 10, S.W. 23, N. 9, E. 21). Hot springs: 2. Forma coronata Ehr. Cl. Syn. 1. c. V. H. Trt. 1. c. fig. 300. 47 samples (S. 10, S.W. 14, NW. 1, E. 21, s. 1. 1). Hot spring: 1. Var. elongatnm W. Sm. Cl. Syn. 1. c. V. H. Syn., Tab. XXIII, fig. 22. Skaftafellssysla (S.) St., Vallanes (E.), H.Js. Forma jmsilla Grim. Cl. Syn. 1. c. V. H. Syn. 1. c. fig. 19. 11 samples (S. 1, S.W. 1, E. 9). Forma trigonocephala Ehr. Cl. Syn. I. c. V. H. Syn. 1. c. fig. 18. 9 samples (S.W. 3, N. 6). Hot springs: 2. Area for Gomph. acum. with var. : Eur., At'., As., Am., Grl. Gomphonema angustatum Kt/. var. prodnctnm Grim. Cl. Syn. I, 181. V. H. Trt., Tab. VIII, fig. 314 (G. ang.). 87 samples (G. Must.). 14 samples (S. 1, S.W. 3, N. 2, E. 8). Area : Eur., Af., As., B. E., Spb. Gomphonema subtile Ehr. Cl. Syn. I, 182. V. H. Trt., Tab. XXIX, fig. 811. Hornafjordr (E. St., Vallanes (E.) H. Js. Area: Eur., Am. FRESH-WATER DIATOMS FROM ICELAND 23 Naviculae minusculae Cl. 1895. Cl. Syn. II, 3. Navicula Atomus Nsegeli var. circiilaris 0st. 0st. Koss., 84, Tab. I, fig. 10. Apavatn ( S. A. F., Reykjavik (SAY) H. Js. Area: As. *Navicula lucidula Grun. Cl. Syn. II, 4. V. H. Syn.,Tab.XIV, fig.40. Apavatn (S.) A. F., Husavik (N.) B. P. - Area: Eur., As., Grl. Navicula minuscula Grun. Cl. Syn. II, 4. V. H. Syn., Tab. XIV, fig. 3. Hvita (S.) A. F. Area: Eur., As. Navicula pelliculosa (Breb.) Hilse. Cl. Syn. II, 3. V. H. Syn, Tab. XIV. fig. 32. Skeidararsandur (S.W.) St. Area: Eur. Anomoeoneis Pfitzer 1871. Cl. Syn. II, 5. Anomoeoneis brachyura (Breb.) Grun. Cl. Syn. II, 7. V. H. Syn., Tab. XII, figs. 8 9 (Nav. serians minor & minima). 8 samples (S. 4, E. 4). Area: Ubiquist. Anomoeoneis exilis (Ktz.) Grun. Cl. Syn. II, 8. V. H. Trt., Tab. IV, fig. 198. 11 samples (S.W. 9, E. 2). Hot spring: 1. Area: Eur., Grl. Anomoeoneis sculpta (Ehr.) Cl. Cl. Syn. II, 6. V. H. Trt., Tab. IV, fig. 194 (Nav. sculpt.). Reykjavik (3 samples) H. Js. Area: Ubiquist. Anomoeoneis sphaerophora (Ktz.) Cl. Cl. Syn. II, 6. V. H. Trt., Tab. IV, fig. 195 (Nav. sphaer.). Reykjavik (S.W.) H. Js. Area: Ubiquist. Anomoeoneis zellensis (Grun.) Cl. Cl. Syn. II, 7. V. H. Syn., Tab. XII, fig. 14 (Nav. zell.). Reykjavik (S.W.) C. H. O. In a hot spring. Area: Eur., Grl. Naviculae heterostichae Cl. 1895. Cl. Syn. II, 8. Navicula cocconeiformis Greg. Cl. Syn. II, 9. V.H.Trl., Tab. XXVII, fig. 729. 13 samples (S. 3, S.W. 7, N.I, E. 2). Area: Eur., As., Am., Grl., J. M., B. E., Spb. 24 ERNST 0STRUP Naviculae lineolatae Cl. 1895. Cl. Syn. II, 10. Navicula anglica Ralfs. Cl. Syn. II, 22. V. H. Trt., Tab. Ill, fig. 136. 25 samples S. 7, SW. 6, N. 6, E. 6). Hot springs: 2. Area: Eur., Af., As., Am., Grl. Var. minuta Cl. Cl. Syn. 1. c. 0st. Koss., Tab. I, fig. 5. Skeidararsandur (S.) St., Ulfjolsvatn (S.1 A. F. Area: Eur.. As., Am., B. E. Var. subsalsa Grim. Cl. Syn. 1. c. V. H. Trt., Tab. Ill, fig. 137. 10 samples (S.I, S.W. 2, N.W. 2, E. 5). Area: Eur., Grl. Navicula anguste-fasciata sp. nov., Tab. nost. Ill, fig. 30. Long: 43 //, lat: 9 /<, str. 12 in 10 />, indistincte punctatis. Valva linear!, apicibus late rostratis. Extremitatibus medianis raphes in eandem partem vergentibus. Raphe mediam partein valvse versus area hyalina, sensim patescente et fasciam angustam efficiente, cincta. Striis radiantibus, apices versus convergentibus. Stadastadur S.W. H. .1. Navicula Boyei sp. nov., Tab. nost. Ill, fig. 31. Long: 14 //, lat: 7 //, str. 12 in !()//. Valva late-lanceolata, apicibus truncatis. Striis debilissimis et vix perspiciendis, media in parte valvae paululum spatiatis, apices versus densioribus, radiantibus et per lotam valvam raphen attin- gentibus. Hallormstadr (E.) B. P. Navicula cincta Ehr. Cl. Syn. II, 16. V. H. Trt., Tab. Ill, fig. 105. 49 samples (S. 11, S.W. 18, N.W. 1, N. 8, E. 10, s. 1. 1). Hot springs: 2. Area: Eur., Af., As., Am., Grl., J. M.. B. E., Fz. J. Var. angusta Grun. Cl. Syn. II, 17. V. H. Syn., Tab. VII, fig. 17. Reykjarfjord (N.W.)? In a hot spring. Area: Eur., As., Am., Aust. Var. Heufleri Grun. Cl. Syn. II, 16. V. H. Trt., Tab. Ill, fig. 106. Arnafellskvisl (S.) St. Area: Eur., Af., Am. Navicula cryptocephala Ktz. Cl. Syn. II, 14. V. H. Trt., Tab. Ill, fig. 122. 53 samples (S. 25, S.W. 15, N. 3, E. 9, s. I. 1). Hot springs: 2. Area: Eur., Af., As., Am., Grl. Var. exilis Ktz. Cl. Syn. 1. c. V. H. Trt. 1. c., fig. 124. 25 samples (S. 10, S.W. 11, N. 2, E. 1, s. 1. 1). Hot spring: 1. Area: Eur., As., Am. FRESH-WATER DIATOMS FROM ICELAND 25 Navicula curte-striata sp. nov., Tab. nost. Ill, fig. 32. Long: 22 //, lat: 7 /i, str. 10 in 10 /<, subtiliter punctatis. Valva elliptice-lanceolata. Extremitatibus medianis raphes in eandem partem vergentibus. Striis marginalibus, aream apicalem latam lanceolatam relinquentibus, leniter radiantibus, apices versus convergentibus. Ingjaldsholl (S.W.) H. Js. Navicula dicephala (Ehr.) W. Sm. Cl. Syn. II, 21. V. H. Trl., Tab. Ill, fig. 138. 56 samples (S. 8, S.W. 16, N. 12, E. 19, s. 1. 1). Hot springs: 7. Area: Eur., Af., As., Am., Grl. Var. undulata var. nov., Tab. nost. Ill, fig. 33. Long: 25//, lat: 8 /<, str. 10 in 10 //. Valva triundulata, ceterum ut in typo. Torfastadir (S.) A. F. In a hot spring. This form has nothing to do with Nav. Motshii Meist. (Schw. 147, Tah. XXII, fig. 16), neither with Nav. Integra W. Sm. var. gibba Pant, in Pant. Bal. 47, Tab. V, fig. 113. Navicula exilior sp. nov., Tab. nost. Ill, fig. 34. Long: 13 //, lat: 4 //, str. 10 in 10 //. Valva anguste-elliptica. Raphe area hyalina angusta cincta. Striis per totam valvam radiantibus. Reykir (S.) A. F. Navicula Gastrum Ehr. Cl. Syn. II, 22. V. H. Trt., Tab. Ill, fig. 134 (the two first figs.). Hvita (S.) A. F. Ubiquist, Grl. Var. exigua Grim. Cl. Syn. II, 23. V. H. Trt. 1. c. 3rd fig. 10 samples (S. 7, S.W. 1, N. 1, E. 1). Area: Eur., Aust. Navicula gracilis Ehr. Cl.Syn. II, 17. V. H. Trt., Tab. Ill, fig. 109. Laugafells Laug (N.) St., Hornafjordr (E.) St. Hot spring: 1. Area: Eur., Af., As., Am., Grl. Var. schizonemoides M. V. H. Cl. Syn. 1. c. V. H. Trt. 1. c., fig. 110. 8 samples (S. 5, E. 3). Hot spring: 1. Area: Eur. Navicula hungarica Grun. Cl. Syn. II, 16. Grim. Oest. Ung., Tab. XXX, fig. 42. 7 samples (S. 2, S.W. 3, N. 1, E. 1). Area: Eur., As., Am., B. E. 26 ERNST OSTRUP Var. capitata Ehr. Cl. Syn. 1. c. V. H. Trt., Tab. Ill, fig. 127 (Nav. humilis). 7 samples \S.\V. 5, N. 2). Hot spring: 1. Area: Eur., As., B. E. Navicula Fustis sp. nov., Tab. nost. Ill, fig. 3f>. Long: 46,, lat: 6,4 /<, str. 12 in !()//. Valva linear!, apicibus leniter attenuatis. Raphe obliqua, area hyalina angusta cincla. Striis per totam valvam radiantibus. Egilstadir (E.) B. P. Navicula islandica sp. nov., Tab. nost. Ill, fig. 36. Long: 22 //, lat: 8 //, str. 20 in 10 //, subtiliter punctatis. Valva elliptica. Raphe area hyalina, medium partem valvse versus aliquantulum dilatata, cincta. Striis per totam valvam radi- antibus, medianis duabus valde spatiatis. Saevarendi (E.) B. P. Navicula Jonssoni sp. nov., Tab. nost. Ill, fig. 37. Long: 23 //, lat: 8 //. Valva elliptica, apices rostratos versus attenuata. Raphe area hyalina angustissima cincta. Striis subtilissimis et, quoad perspicere potui, per totam valvam radiantibus. Hafnarholmi (E.) H. Js. Possibly this form is related to, but not identical with Nav. crypto- cephala var. latior Jul. Dannf. in Diat. o. t. Bait. p. 26, Tab. II, fig. 12. Navicula lanceolata (Ag.) Ktz. Cl. Syn. II, 21. V. H. Trt., Tab. Ill, fig. 139. Thjorsa (S.) A. F., Sta&astadur fS.W.) H. Js. Area: Eur., Af., Am., Aust., Grl. Var. Cijmbiila Donk. Cl. Syn. II, 22. V. H. Syn., Tab. VII, fig. 32. 4 samples (S.W. 3, E. 1). Area: Eur., As. Var. latior Dannf. Cl. Syn. I.e. Dannf. Bait., Tab. II, fig. 12 (N. cryptoc. lat.). Laxa (S.) A. F. Area : Eur. Var. phylleptu Ktz. Cl. Syn. 1. c. V. H. Trt., Tab. Ill, fig. 141. Thorsa (S.) A. F. Area: Eur. Navicula ludloviana A. S. Cl. Syn. II, 24. A. S. Atl., Tab. XLVI, fig. 15. 7 samples (S. 2, S.W. 1, E. 4). Area: Am. FRESH-WATER DIATOMS FROM ICELAND 27 Navicula lyrigera sp. nov., Tab. nost. Ill, fig. 38. Long: 20 //, lat: 11 //, str. 20 in 10 //. Valva late lanceolata, apicibus attenuatis. Raphe area byalina angusta cincta. Striis debilissimis, difficiliter perspiciendis, utroque in latere ita abruptis, ut figura lyraeformis, male autem definita, existat. Fresh-water sampl. : Grimsey (N.) O. D., Marine sampl.: Skerjafjordur (S.W.) H. Js., Thorisholmi (SAY.) H.Js. This form has some resemblance to Navicula bifissa A. S. in A. S. All, Tab. CCXII, fig. 33, but it is much more closely striated, and the lateral areas are not so distinctly defined. Nav. bifissa is from Yokohama (therefore probably a marine form). As regards Nav. lyrigera, I have found it in 3 samples, of which one is a fresh -water sample solely containing fresh-water forms; the two others are salt-water samples, both however mixed with fresh- water forms; for this reason I have considered it best placing it as a fresh-water form. *Navicula oblonga Ktz. Cl. Syn. II, 21. V. H. Tit., Tab. Ill, fig. 100. Sydri Gardar (S W.) H.Js., Sta6asta^ur (S.W.) H.Js. Area: Ubiq. Navicula Ostenfeldi sp. nov., Tab. nost. Ill, fig. 39. Long: 24 //, lat: 4 //. Valva anguste- lanceolata, apicibus capitatis. Raphe media in parte valvse area hyalina longina cincta. Striis inconspicuis. Krisuvik (S.) C. H. O. Navicula peregrina Ehr. Cl.Syn.II, 18. V. H. Trt., Tab. Ill, fig. 101. 8 samples (SAY. 6. N. 1, E. 1). Area: Eur., Af., As., Am. Var. Menisculus Schum. Cl. Syn. 1. c. V. H. Trt. 1. c., fig. 103. 4 samples (S. 1, SAY. 2, E. 1). Area: Eur., Af., As., Am. Var. Meniscus Schum. Cl. Syn. 1. c. V. H. Trt. 1. c., fig. 102. 6 samples (S. 1, S.W. 2, N. 2, E. 1). Hot spring: 1. Area: Eur., Af., As., Am., Grl. Var. polaris Cl. Syn. 1. c. Lgst. Spb., Tab. II, fig. 3. Reykholt (SAY.) H. Js., Grimsey (N.) O. D. Area: Eur., Grl., B. E., Spb. In a sample from Hanefsstadaeyrar (E.) H. Js., I have found a Nav. pereg. with 12 strise on 10 // being thus more closely striated than the typical form. Navicula pinnularioides sp. nov., Tab. nost. Ill, fig. 40. Long: 36 //, lat: 6,4 //, str. 8 in 10 //. Valva lineari apices rostratos versus attenuata. Raphe area hyalina satis lata cincta. Striis per totam valvam radiantibus, in 28 ERNST 0STRUP medio uno in latere valvse deficientibus ibique fasciam unilateralem satis latam relinquentibus. Fljotsdalur .) B. P. When I place this form under Nav. lineolatse, it is owing to the striae which, by great enlargement, assume the peculiar "woollen" ap- pearance, indicating a finer structure. *Navicula radiosa Ktz. Cl. Syn. II, 17. V. H. Trt., Tab. Ill, fig. 112. 286 samples (S. 66. S.W. 77. X.W. 4, N. 38, E. 97. s. 1. 4 . Hot springs: 8. Area: Eur., Af.. As.. Am., GrL B. E.. Spb. *Navicula Reinhardti Grun. Cl. Syn. II, 20. V. H. Trt., Tab. Ill, fig. 132. 5 samples (S. 3, N. 1, E. 1). Area: Eur., As., Am., GrL B. E. Var. Yenisseyensis Grun. Cl. Syn. 1. c. Cl. & Gr. A. D., Tab. II, fig. 30 (N. digitr. striolata). Alftatjorn E.) B. P. Area: As. Navicula rhyncocephala Kit. Cl. Syn. II, 15. V. H. Trt., Tab. Ill, fig. 119. 21 samples (S. 7, S.W. 10, N.I, E. 2, s. 1. 1). Hot spring: 1. Area: Ubiquist, Grl., B. E. Var. amphiceros Ktz. Cl. Syn. 1. c. V. H. Trt. 1. c., fig. 120. 7 samples (S.W. 6, N. 1). Area: Eur.. Aust. Navicula Salinarum Grun. Cl. Syn. II, 19. V. H. Trt., Tab. Ill, fig. 108. Apavatn (S.I A. F. Skeidararsani)ur (S.) St. Area: Eur., Af.. Am.. Spb. Navicula semifasciata sp. nov., Tab. nost. Ill, fig. 41. Long: 27 //, lat: 9 //, str. 12 in 10 /*, subtiliter punctatis. Valva rhomboidea, apicibus subcapitatis. Raphe area hyalina angustissima, mediam partem valvae versus patescente, ibique in fasciam latam unilateralem dilatata, cincta. Striis radiantibus, apices versus convergentibus densioribusque. Krokur (S.) H. Js. Navicula spatiata sp. nov., Tab. nost. Ill, fig. 42. Long: 16 //, lat: 8 //, str. 14 in !()/*, obscure punctatis. Valva elliptica. Raphe area angusta cincta. Striis medianis valde spatiatis, cetera in parte valvae radiantibus, apices versus leniter curvatis. Apavatn (S.) A. F. FRESH-WATER DIATOMS FROM ICELAND 29 Navicula Thingvallae sp. nov., Tab. nost. Ill, fig. 43. Long: 25 //, lat: 7,2 11, str. 16 in 10 //, subtiliter punclatis. Valva elliptica, apicibus capitatis. Raphe area hyalina angusta, media in parte valvae in fasciam latam dilatata, cincla. Striis radian- tibus, apices versus convergentibus. In fascia striae singular, longae abbreviatseque, adsunt. Thingvallavatn (S.W.) A. F. *Navicula Tuscula Ehr. Cl. Syn. II, 19. V. H. Trt., Tab. IV, fig. 166. 6 samples (S.W. 1, X. 2, E. 3). Area: Eur., Af., As., Am., Grl., B. E., Spb. Var. Strosei 0st. 0st. D. D., 84. Strose Kliek., Tab. 1, fig. 28 (Staur. dilat.). 11 samples (S. 4, S.W. 5, N.I. E.I). Area: Eur. Navicula viridula Ktz. Cl. Syn. II, 15. V. H. Trt., Tab. Ill, fig. 115. 12 samples S.W. 2, N. 9, E.I). Area: Ubiquist. Var. slesuicensis Grim. Cl. Syn. 1. c. V. H. Trt. 1. c., fig. 116. 74 samples (S. 23, S.W. 20, N.W.I, N. 14, E. 16). Hot springs: 2. Area : Eur., Grl. Navicula vulpina Ktz. Cl. Syn. II, 15. V. H. Trt., Tab. Ill, fig. 111. 9 samples iS. 2, S.W. 3, E. 4). Area: Eur., As., Am., Aust., Grl. Naviculae punctatae Cl. 1895. Cl. Syn. II, 37. *Navicula amphibola Cl. Cl. Syn. II, 45. Lgst. Spb., Tab. II, fig. 7 (Nav. punct. asym.). 24 samples (S. 1, S.W. 2, N. 6, E. 15). Area: Eur., As., Am., Grl., B. E., Spb., Fz. J. Navicula lacustris Greg. Cl. Syn. II, 44. Cl. Finl., Tab. II, fig. 14. 4 samples (. 3, E. 1). Area: Eur., Am. Navicula pusilla W. Sm. Cl. Syn. II, 41. V. H. Trt., Tab. IV, fig. 186. 40 samples (S. 5, S.W. 17, N.W. 3, N. 9. E. 6). Hot springs: 5. Area: Ubiquist, Grl., J. M. Pinnularia Ehr. 1843. Cl. Syn. II, 71. Gracillimce Cl. 1895. Cl. Syn. II, 74. Pinnularia gracillima Greg. Cl. Syn. II, 74. V. H. Syn., Tab. VI, fig. 24 (Nav. grac.). 6 samples (S. 3, S.W. 2, E. 1). Area: Eur., As., Grl., J. M., Fz. J. 30 ERNST 0STIUI' Pinnularia leptosoma Grun. Cl. Syn. II. 74. V. H. Syn., Tab. XII, fig. 29 (Nav. lept.). 6 samples (S.W. 4. X. 2). Hot springs: 3. Area: Eur.. Grl. Var. nndnlata var. nov., Tab. nost. Ill, fig. 44. Long: 42 //, lat : 5,4 //, str. 16 in If)//. Valva lineari, leniter undulata. Raphe area hyalina angusta, media in parte valva' in fasciam satis lalam dilatata, cincta. Striis subradiantibus. apices versus convergentibus. Myvatn (N.) Rd. Pinnularia molaris Grun. Cl. Syn. II, 74. V. H. Syn., Tab. VI, fig. 19 {Nav. mol.). Hrafnagil (X.) H. Js., Gautavik (E.) H. Js. Hot spring: 1. Area: Eur., As.. Am., Aust. Pinnularia sublinearis Grun. Cl. Syn. II, 74. V. H. Trt., Tab. II, fig. 78 (Nav. subl.). 15 samples (S. 2, S.W. 3. X. 4. E. r, . Area: Eur., Grl., J. M. Cnpitatce Cl. 1895. Cl. Syn. II, 75. *Pinnularia appendiculata Ag. Cl. Syn. II, 75. V. H. Trt., Tab. II, fig. 93 (Nav. app.). 19 samples S. 3. S.W. 10, X.I, E. 5). Hot springs: 2. Area: Ubiquist, Grl. Var. budensis Grun. Cl. Syn. 1. c. V. H. Syn., Tab. VI, figs. 2728 (Nav. app. bud.). Grafarbakki (S.) A. F., Hrafnagil (X.) H. Js., Stutfell (E.) B. S. Hot springs: 2. Area: Hot springs, Eur., Xew Zealand. *Pinnularia Brauni Grun. Cl. Syn. II, 75. V. H. Trt., Tab. II, fig. 95 (Nav. Br.). Brunavikurstrand (E.) H. Js. Area: Ubiquist. Pinnularia interrupta W. Sm. f. stauroneiformis Cl. Cl. Syn. II, 76. V. H. Trt., Tab. II, fig. 97 (Nav. mesolepta Termes). 30 samples (S. 4. S.W. 13, X.W. 1, X. 9, E. 3). Hot springs: 5. Area: Eur., As., Am., Aust., Grl. F. biceps Cl. Cl. Syn. I. c. Lgst. Spb., Tab. 1, fig. 5 (Nav. bi- capitata). 10 samples (S. 1, S.W. 4. X. 1, E. 4>. Area: Eur, As., Am., Aust., Grl., Spb., Fz. J. FRESH-WATER DIATOMS FROM ICELAND 31 Pinnularia mesolepta Khr. var. (ingusta Cl. Cl. Syn. II, 76. A. S. Atl., Tab. XLV, fig. 62 (Nav. gracillima). 17 samples (S. 3, S.W. 5, N.W.I, N. 3, E. 5). Hot spring: 1. Area : Eur., Am. Var. polyonca Breb. Cl. Syn. 1. c. V. H. Trt., Tab. II, fig. 99. 10 samples (S.I, S.W. 5, E. 4). Area : Eur. Var. stauroneiformis Grun. Cl. Syn. 1. c. A. S. Atl., Tab. XLV, figs. 5253. 55 samples (S. 11, S.W. 20, N.W.I, N. 5, E. 18). Hot springs: 5. Area: Eur., Af., Am., Grl., J. M., F. J. Pinnularia microstauron Ehr. Cl. Syn. II, 77. V. H. Syn, Tab. VI, fig. 9 (Nav. biceps hybrida). 11 samples (S. 3, S.W. 2, N.W.I, E.I). Hot spring: 1. Area: Ubiquist, Grl., J. M., Spb., Fz. J. Pinnularia Oculus 0st. 0st. 0stg. Ferskv., 269, Tab. I, fig. 6. 7 samples (S. 1, S.W. 1, N. 1, E. 4). Area: Eur., Grl. Pinnularia perexilis sp. nov., Tab. nost. Ill, fig. 45. Long: 17 //, lat: 2,7 //. Valva linearis, in medio inflata, apicibus capitatis. Striis sub- lilissimis et, quoad perspicere potui, per totam valvam radiantibus, media in parte valvse aliquantulum spatiatis. Laugaa (S.W.) A. F. In spite of the striation radiating all throughout, at least as far as I can see. 1 consider that .this small form requires its place among Finn, capitatae. Pinnularia subcapitata Greg. Cl. Syn. II, 75. V. H. Trt., Tab. II, fig. 91 (Nav. subc.). 51 samples (S. 11, S.W. 16, N.W.I, N. 8, E. 15). Hot springs: 2. Area: Ubiquist, Grl., J. M., Spb., Fz. J. Var. paucistriata Grun. Cl. Syn. 1. c. V. H. Trt. 1. c,, fig. 92 (Nav. sub. pauc.). Hvita (S.) A. F. Area: Eur. Divergentes Cl. 1895. Cl. Syn. II, 77. *Pinnularia Brebissoni Ktz. Cl. Syn. II, 78. V. H. Trt., Tab. II, fig. 82 (Nav. Breb.). 34 samples (S.I, S.W. 9, N. 6, E. 17, s. I. 1). Hot spring: 1. Area: Eur., Af., As., Am., Grl., J. M., Spb. 32 ERNST 0STRIP *Var. dimimita H.V. H. Cl.Syn. 1. c. V. H.Trt. 1. c., fig. 84 (X.Breb. dim.). 8 samples S. 1. SAY. 1, X. 1, E. 4, S. L. 1). Hot spring: 1. Area: Eur., Am.. Grl. Var. linearis O. M. O. M. Rieseng., 25, Tab. Ill, fig. 12. Yttri Skc')gar iS. , H. Js. Area: Eur. Pinnularia bryophila sp. nov., Tab. nost. Ill, fig. 46. Long: 43 ,, lat: 9,6 //, str. 12 in 10 u. Valva lineari, apicibus rotundatis. Raphe area hyalina lata, media in parte valvae, in fasciam. in qua uno in latere stria singula adest, dilatata cincta. Fissuris terminalibus et extremitatibus me- dianis raphes in partes diversas inclinantibus. Striis radiantibus, apices versus convergentibus. Sey. V. II. Trl., Tab. II, fig. (if). HornarfjonV (E.) St. Area: Km*., Af., Am. :|: Mastogloia Smith! Thw. var. lacustris (irun. Cl. Syn. II, 152. V. II. Trt., Tab. II, fig. (Jl. Ilrossholl (SAY.) A. F., in a hot spring. Area: Eur., Spb. Monoraphidese Achnantheae Cl. 1895. Cl. Syn. II, 16,'}. Rhoicosphenia Grim. 18(50. Cl. Syn. II, 1C.."). Rhoicosphenia curvata (Ktx.) Grun. Cl. Syn. II, K>5. V. H. Tit., Tab. VII, iig. 31!). 86 samples ;S. 39, S.W. 17. X.W.2, N. 1C.. E. 1 1 , s. 1. 1). Hot springs: 9. Area: L'biquist, Grl., Spb., Fz. J. Cocconeis (Ehr. 1835) Grun. 18C>8. Cl. Syn. II, 108. Subgenus Cocconeis Cl. 1895. Cl. Syn. II, 1()8. Cocconeis Placentula Ehr. Cl. Syn. II, 169. V. H. Trt., Tab. VIII, fig. 341. 120 samples (S. 44, S.W. 37, X.W. 1. X. 18, E. 25, s. 1. 1). Hot springs: 7. Area: Ubiquist. Subgenus Encocconeis Cl. 1895. Cl. Syn. II, 173. Cocconeis flexella Ktx. Cl. Syn. II, 179. V. H. Trt., Tab. VIII, fig. 322 (Achnanthidium (lex.). : 1 samples (S.I. S.W. 20, X. 5, K. 21, s. 1. 1 . Hot springs: 2. Area: Eur., At'., As., Am. Var. intermedia 0st. 0st. D. Exp. 244, Tab. XIV, fig. 12. Unai'.s E.'' II. .Is. Area: Grl. Cocconeis minuta Cl. Cl. Syn. II, 179. Lgst. Spb., Tab. II, fig. 1(> (C. Tlnvaitesi v. arctica). 4 samples ^S. 1, S.W. 3). Are:i: Em-.. Grl., Spb., Fs. J A FRESH-WATER DIATOMS FROM ICELAND 41 Var. alpestris Br. Cl. Syn. II, 180. Le Dial. II, Tab. V, fig. 15. Hof (N.), Gautavik (E.) II. Js. Area: Eur., Grl. Subgenus Microneis Cl. 1895. Cl. Syn. II, 187. Achnanthes affinis Grun. Cl. Syn. II, 190. V. H. Trt., Tab. VIII, fig 329. Thingvellir (S.W.) K. W. & Ho. Area: Eur., Am., Aust. Achnanthes Biassolettiana Ktz. Cl. Syn. II, ISO. V. H. Trt., Tab. VIII, fig. 331. 24 samples (S. 4, S.W. 4, N. 3, E. 12, s. I. 1). Area: Eur., Am., J. M. Achnanthes Boyei sp. nov., Tab. nost. IV, fig. 60. Long: 30 //, lat: (i //, sir. 12,5 in 10 /(, subtiliter punctatis. Valva anguste lanceolata, paululuin asymmetrica. Hypotheca: Raphe area hyalina angusta, media in parte valvse in fasciam latam dilatata, cincta. Striis per tolam valvam radiantibus. Epitheca: Striis media in parte valvse uno in latere deficientibus, allero in latere panlulnm abbreviatis. Ceterum forma hypothecse simili. 4 samples (N. 3, E. 1 ), all B. P. :i: Achnanthes delicatula Ktz. Cl. Syn. II, 190. V. H. Trt., Tab. VIII, fig. 330. SpoastaMr (S.) A. F., Eidistjorn (S.W.) C. H. O. Area: Eur., Af, As., Grl. Achnanthes exigua Grun. Cl. Syn. II, 190. V. H. Syn., Tab. XXVII, figs. 2930. 7 samples (S. 3, S.W. 4). Hot spring: 1. Area: Ubiquist. i: Achnanthes exilis Ktz. Cl. Syn. II, 189. V. H. Trt., Tab. VIII, fig. 333. Reykjavik (S.W.) C. H. O., in a hot spring. Area: Eur., Af., As. Achnanthes linearis W. Sm. Cl. Syn. II, 188. V. H. Trt. ; Tab. VIII, fig. 335. 4 samples (S. 1, X. 2, E. 1). Area : Eur., As.. Am., Grl., Fz. J. Achnanthes minutissima Ktz. Cl. Syn. II, 188. V. H. Trt., Tab. VIII, fig. 334. 27 samples (S. 4, S.W. 11, N. 3, E. 8, s.l. 1). Hot springs: 3. Area: Eur., Af., As., Am., Grl., J. M., B. E., Spb. 42 ERNST (JSTRUP 1'inlcr A. minut. I include vnr. cryptocephala (cnfr. Cl. 1. c. . which can hardly he kept apart from the typical species. Achnanthes tylophora (Rcichelt) Cl. Reich. Schohsee, 199(Stauron. lyl.), A. S. All., Tab. CCXLII, figs. 17-18 (Achn. exigua). Apavatn S.. two samples) A. F. Area: Eur. Suligenus Achnanthidinm (Kt/. 1844) Heib. 1863. Cl. Syn II, 191. Achnanthes Calcar Cl. Cl. Syn. II, 174. Cl. Finl., Tab. Ill, fig. 8. 6 samples ;S. 2. SAY. 1, N. 2. E. 1). Area: Eur. Clcve places this species under "Eucocconeis". YVhen I have moved it from there, it is owing to the horseshoe marking, which, it seems to me, approaches it to the group of Achn. lanceolata. Achnanthes coarctata (Bres.) Cl. Syn. II, 192. V. H. Trt., Tab. VIII, fig. 327. 39 samples (S. 9. SAY. 8, NAY. 1, X. 6, E. 13, s. 1. 2). Hot spring: 1. Area: Eur., Af.. As.. Am.. Grl.. J. M., B. E., Spb. I have given a figure of a square form of A. coarctata on Tab. nost. IY, fig. 61. It resembles somewhat the A. coarct. elineata Lgst., figured in O. M. Pat., Tab. 1, iig. 8, which variant, however, is referred by Cleve, 1. c. to the typical species. I found it in a sample from Yik (S.) H. Js. 'Achnanthes lanceolata Brt-b. Cl. Syn. II, 191. V. H. Trt., Tab. VIII, fig. 336. 140 samples (S. 53, SAY. 29, NAY. 10, N. 10, E. 38). Hot springs: 9. Area: Ubiquist. Var. capitatfi O. M. O. M. Pat., 8, Tab. I, figs. 67. Krokur (S.) H. Js., Skutustadir (E. two samples) B. H. Area: Am. Var. tlnhid C.run. Cl. Syn. II, 192. V. H. Trt., Tab. VIII, fig. 337. Apavatn (S.) A. F. Area: Eur., Am. Var. elliptica Cl. Cl. Syn. 1. c. Cl. Finl., Tab. Ill, figs. 10-11. Apavatn (S.; A. F.. Hornafjorfir (E.) St. Area: Eur. Yar. fceroensis 0st. 0st. Faer. Frcsbw. 277, Iig. 44. :.,X samples S. 22. SAY. 7, NAY. 1, N. 1, E. 17, s. 1. 3). Hot springs: 2. Area : Eur.. H. E. Var. subin/ltila var. nov., Tab. nost. IV, Iig. 62. Long: 15//, lat: 4 //, sir. 14 in 10 //. Valva lincari, in medio paululum inflata, apicibus rotunclatis. Striis per tolain valvam radiantibus. FRESH-WATER DIATOMS FROM ICELAND 43 Hypotheca: Striis media in parte valvae deficientibus , ibique fasciam latam relinquentibus. Epitheca: Uno in latere media? partis valvse spalium hyalinum, solere equinse inslar, adest. Egilstaftr (E.) B. P., Hornafjordr ;E.} St. This small form is hardly identical with Hustedt s Ach. lane, ven- tricosa (cnfr. Hnst. Slid. 64, Tab. II, fig. 321; it seems to me, it should rather be placed close to Ach. lane, freroensis. Achnanthes Peragalli Brim & Herib. Cl. Syn. II, 192. 0sl. D. D.. Tab. IV, fig. 85. Apavatn (S.) A. F., ilfjolsvatn (S.) A. F. Area: Eur. Achnanthes rhyncocephala A. Cl. A. Cl. Finl., 43, Tab. IV, fig. 85. Husavik (N.) B. P., Grimsa (E.) B. P. Area : Eur. Kalyptoraphideae Eschatoraphideae Surirella Turpin 1827. V. H. Trt., 368. Surlrella asymmetrica sp. nov., Tab. nost. IV, fig. 63. Long: 40 /<, lat: 10 /. Valva elliptice-lanceolata, margine una recta, altera autem con- vexa. Area apicali angusta. Canaliculis in margine recta omnino 14, in margine convexa omnino 7. In a flowing off from Geysir (S.W.) A. F. *Surirella biseriata Breb. V. H. Trt., 369, Tab. XII, fig. 575. 34 samples (S. 6, S.W. 8, N.W.I, N. 7, E. 12). Hot springs. Area: Eur., Af., As., Am. Surirella Engleri O. M. f. angustior. O. M. Nyassa, 28, Tab. 1, fig. 5. A. S. Atl. CCXLV, fig. 14. Laugavatn (S.) B^P. MoSruvellir (S.W.) B. P. Area: Af. Surirella granulata 0st. var. elliptica var. nov., Tab. nost. IV, fig. 64. Long: 72 /<, lat: 20 //, canalic. 2,7 in 10 u. Valva elliptica, irregulariter punctata, area apicali angustissima. Reykjavik (S.W.) C. H. O. This form answers in even 7 respect, except by the exterior contour, to Sur. granulata 0st. in Ost. Koss. 91, Tab. II. fig. 17. 44 ERNST 0STRUP Surirella islandica sp. nov., Tab. nost. IV, fig. 6.1. Long: 28 it, lat: 7 //, canalic. 5 in !()//. Valva lineari-elliptica, canaliculis marginalibus. Vnllanes (E/) 13. P. This small form reminds somewhat of the S. minuta Breb.. figured in Pant. Bal., Tab. XI, fig. 286. As to the claim of this appellation see besides O. M. Pat., pag. 37-38. Surirella Jonssoni sp. nov.. Tab. nosl. IV, fig. 66. Long: 81 //, lat: 9 //, canaliculis 5,5 in 10 //. Valva linear!, delicatissime transverse lineata, apicibus cuneatis. Linea apicalis vix conspicua adesl. Desjamyri (E.) H. .Is. This form is possibly related to, though hardly identical with Sur. gracilis Grim., V. H. Syn., Tab. LXXIII. fig. 16, which shows a similar transversal striation of very fine rows of puncta. Surirella linearis W. Sm. V. H. Trt., 369. A. S. All., Tab. XXIII, fig. 27. 21 samples (S. 3, S.W. 5, X. 7, E. 6). Area : Eur., Af., As., Am., Spb. Var. conslriclu Grun. De Toni Syll., 568. A. S. All., Tab. XXIII, fig. 28. 8 samples (S.I, S.W. 2, N. 2, E. 3). Area : Eur., Am. Surirella Molleriana Grun. 0st. F?er. Freshw. 285, fig. 49. A. S. All., Tab. LVI, figs. 2122. 1 1 samples (S. 1, S.W. 5, N. 2, E. 3). Area: Eur., As., Am. Surirella ovalis Bivb. var. angusta Ktz. V. H. Trl. 373, Tal). XIII, fig. 590. 21 samples (S. 3, S.W. 5, N. 3, E. 10). Area: Eur., Af., As., Am., Grl., Spb., F/. .1. Var. minuta Brrb. V. H. Trt. 1. c., Tab. c., fig. 588. 23 samples (S.I, S.W. 5, N. 3, E. 14 . Hot springs: 2. Area: Eur., Af., As., Am., C.rl., H. E. Tar. ovata Ktz. V. II. Trt. 1. c., Tab. c., fig. 587. 97 samples (S. 34, S.W. 28, N.W. 2, N. 1 (1. E. 17). Hot springs: 5. Ari-n: Kur., Af., As, Am.. Grl., H. E., Spb., K/. J. I have found nearly circular forms of Ibis variant in t\vo samples from Borg S.W. B. P'., Slutnes N.) B. P. Var. pimmta W. Sm. V. H. Trt. 1. c., Tab. c., fig. 591. :i( samples (S. 0, S.W. 9, N.W. 1, N. 3, E. 14\ Area: Eur., Spb. FRESH-WATER DIATOMS FROM ICELAND 45 Var. pandnriformis W. Sm. W. Sm. Syn. I, 33. V. H. Syn., Tab. LXXIII, fig. 11. 11 samples (S. 4, SAY. 2, E. 5). Area: Kur. Surirella robusta Ehr. V. H. Trt. 371, Tab. XII, fig. 577. A. S. All., Tab. XXIII, fig. 3 (Sur. rob. valida). Laugarvatn (S., two samples) B. P. Area: Eur. Var. splendida Ktz. V. H. Trt. 1. c., Tab. c., fig. 578. Apavatn (S.) B. P. Area: Eur., Af., Am. Surirella turgida W. Sm. V. H. Trt. 372, Tab. XXXI, fig. 867. Thingvallavatn (S.W.) C. H. O. Area: Eur. Stenopterobia Breb. in litteris. Hust. Sur., 114. * Stenopterobia intermedia Lewis. Hust. Sud., 115. Lew. interm. F., Tab. 1, fig. 2 (Surirella interm.). Reykjavik (SAY.) H. Js. Area: Eur., Af., Am., Grl. Campylodiscus Ehr. 1841. V. H. Trt., 375. *Campylodiscus hibernicus Ehr. var. noricus Ehr. V. H. Trt. 379, Tab. XIV, fig. 594. 6 samples (S. 1, SAY. 2, N. 2, E. 1). Area: Eur., B. E. On tab. nost. IV, fig. 67, I have given a delineation of a fragment of a Campylodiscus, which I have not been able to refer to any species known by me. It was found in a "small waterhole near Geitaberg". Cymatopleura W. Sm. 1851. V. H. Trt., 366. :|: Cymatopleura elliptica (Breb.) W. Sm. V. H. Trt. 367, Tab. XII, fig. 480 b. 10 samples (S. 1, SAY. 4, N. 2, E. 3). Area: Eur., Af., As., Am. *Cymatopleura Solea (Breb.) W. Sm. V. H. Trt. 367, Tab. XII, fig. 482 b. 52 samples (S. 20, SAY. 11, N. 4, E. 17). Hot springs: 2. Area: Eur., Af., As., Am., B. E. 1C) ERNST 0STRUP Tropidoraphideae Hantzschia Grun. 1877. V. II. Trt., 380. "Hantzschia amphioxys (Ehr.) Grun. V. H. Trl. 381 , Tab. XV. fig. 483 1). 17(i samples (S. 31 , S.W. 37, N.W. 2. N. 31, K. 73. s. 1. 2 . Hot springs: 9. Area: Eur., Af.. As.. Am.. Grl. J. M.. B. E.. Sph.. /..!. Var. constricta Pant. Pant. Bal. S. 83, Tab. IX, fig. 141. Vallanes (E.) H. Js. Area: Eur. *Var. elongata Grun. V. H. Trl. 381, Tab. XV, fig. 487 b. 22 samples (S. 2. SAY. 4. N. 2. E. 14). Hot spring: 1. Area: Eur, Af., Am., Aust. Hantzschia dubravicensis Grun. Grun. 0st. Ung. 140, Tab. XXIX, fig. 23. Tab. nost. V, lig. 08. Long: 94 //, lal: 7 /<, punct. carinal. 5 in 10 //, str. 1C) in 10 //, subtiliter punctatis. Margine carinali in medio leniter incurvata, margine allcra fere recta. Lagarfljot (E.) B. P. Area: Eur. Grunow 1. c. places this species as a Hantzschia, but with a query. This is however undoubtedly correct. When I give a figure of it, it is because the form found by me is substantially larger and on the whole somewhat more elegantly built than Grunow' s H. dubrav., but I have no doubt whatever that they are identical. Hantzschia truncata sp. nov., Tab. nost. V, fig. (59. Long: 43 H, lal: 10 11, puncl. carinal. 5,5 in 10 //, sir. 14 in 10 //, punctatis. Yalva hantzschioidea, apicibus curte truncalis. Punclis carina- libus partim confluentibus. Hrafnagil (N.) H. Js.. in a hot spring. Hantzschia virgata (Roper) Grun. var. leplocephala 0st. 0st. D. D. 144, Tab. IV, fig. 9(>. Skei16. 2G samples (S. 2. S.W. 5, X.W. 1. N. 4, H. 13. s. 1. 1). Hot springs: 4. Area : Ear., As., Am., Spb. Dissipatce Grun. 1880. V. H. Trl. 394. Nitzschia dissipata (Ktx.) Grun. V. H. Tit. 394, Tab. XVI, fig. 525. Keldur (S.i A. F.. Hotfabrekka (S.) H. Js.. Thingvallavatn (SAY.) C. H. O. Area: Eur., Af.. As., Am., B. E., Spb. Sigmoidece Grun. 1880. V. H. Trt. 395. *Nitzschia sigmoidea (Ehr.) W. Sm. V. H. Trl. 395, Tab. XVI, fig. 528. 13 samples (S. 2, SAV. 3, N. 5, E. 3). Hot spring: 1. Area: Eur.. Af.. As., Am. Sigmata Grun. 1880. V. H. Trl. 396. 'Nitzschia Sigma W. Sm. V. H. Trt. 396, Tab. XVI, fig. 531. Reykjavik iSAV. in two samples) H. Js. Area: Ubiquisl, Grl. Var. Clansi Hant/scb. Grun. Gasp. S. 119. V. H. Syn., Tab. LXVI , fig. 10 14 samples (S. 10, S.W. 3. N.I). Hot springs. Eur., Grl.. F/. .1. Line-arcs Grun. 1880. V. H. Trl. 398. Nitzschia Kittli Grun. Grun. Oesl. Ung. 155, Tab. XXIX, figs. 24 25. 6 samples (S. 3. S.W. 1, X. 1, I-:. 1). Area: Eur. *Nitzschia linearis (Ag.) W. Sm. V. II. Trl. 399, Tab. XVI, lig. 542 15 samples (S. II, S.W.I. NAY. 1. N.I, F. 3). Hot springs: 2. Area: Fur., Af., As.. Am., Grl. FRESH-WATER DIATOMS FROM ICELAND 49 Nitzschia vitrea Norman var. recta Hentzsch. V. H. Trt. 400, Tab. XVI, fig. 547. Ulfjolsvatn (S.) A. F. Area : Eur., As.. Am., Grl. Var. Salinarnm Grun. V. H.Trt. 399, Tab. XVI, fig. 546. Arnafellskvisl (S.) St., Vestmannaeyjar (S.) St. Area: Eur. In Denmark I have found the identical form in fresh-water (cnfr. 0st. D. D. 161). Nitzschia Oestrupi Pant. Pant. Lac. Peis. 30, Tab. Ill, fig. 145. Arnafellskvisl (S.) St., Skaptafellssysla (S.) St. Pantocsek (1. c.) refers this species to a new section "Constrictae". I think it might very well be placed under "Lineares", closest to N. Kittli. Lanceolate Grun. 1880. V. H. Trt. 400. Nitzschia amphibia Grun. V. H.Trt. 403, Tab. XVII, fig. 563. 55 samples (S. 14, S.W. 17, N. 11, E. 12, s. 1. 1). Hot springs: 17. Area: Eur., Af., Am. Var. acutiuscula Grun. Cl.&Gr. A. D. 98. V. H. Syn., Tab. LXVIII, figs. 1922. Laugarvatn (S.) A. F. Area: Eur., Am., Aust. Var. Frauenfeldi Grun. Cl. & Gr. A. D.98. V. H. Syn., Tab. c., fig. 18. 12 samples (S. 4, S.W. 4, N. 2, E. 2). Hot spring: 1. Area : Eur., Am., Aust. Nitzschia Frustulum (Ktz.) Grun. V. H. Trt., 403, Tab. XVII, fig. 564. 6 samples (S. 3, N.I, E. 2). Hot spring: 1. Area: Eur., Af., Am., Grl., J. M., Spb., Fz. J. Nitzschia glaberrima sp. nov., Tab. nost. V, fig. 73. Long: 64 ju, lal: 3 /<. Valva linear!, apicibus subcapitatis. Structural!) ullam valvse per- spicere non potui. Una in margine valvae autem puncta minutissima et innumerabilia adsunt. Reykjavik (S.W.) H. Js. I consider this form must be placed under "Lanceolatae" possibly nearest to Nitz. gracilis. Nitzschia Hantzschiana Rbh. var. glacialis Grun. Cl. & Grun. A. D. 99. V. H. Syn., Tab. LXIX, fig. (N. Frust. glac.). 7 samples (S.W. 5, E. 2). Area: Eur., Grl., Spb., Fz. J. The Botany of Iceland. Vol. II. 4 50 ERNST 0STRUP Nitzschia Heufleriana Grim. Cl. & Grim. A. D. 90. V. H. Syn., Tab. LXVIII, figs. 1314. Eyj61fssta8ir, Breiflalsa, Holmanes (all E.) H. .Is. Ait-a: Eur., B. E., Fz. J. Nitzschia intermedia Hantzsch. Cl. & Gr. A. D. 95. V. H. Syn., Tab. LXIX, fig. 10. 9 samples (S. 4, SAY. 3, E. 2). Area : Eur., Am. *Nitzschia Kiitzingiana Hilse. Cl. & Gr. A. D. 96. V. H. Syn., Tab. LXIX, figs. 2426. Hornarfjordr (E.) St. Area: Eur., Am., B. E. Nitzschia mucronata sp. nov.. Tab. nosl. V, fig. 74. Long: 18/f, lat: 2 ft. Valva anguste-lanceolata, apicibus acutis. Punctis carinalibus minutissimis innumerabilibusque. Structuram ullam valvae perspicere non potui. Minni Laxa (S.) A. F. Nitzschia Palea (Ktz.) W. Sm. V. H. Trt. 401, Tab. XVII, fig. 514. 83 samples (S. 26, S.W. 23, N.W. 2, N. 14, E. 16, s.1.2). Hot springs: 2. Area: Eur., Af., As., Am., Fz. J. Var. fonticola Grun. V. H. Trt. 402, Tab. c., fig. 557. 6 samples (S. 3, S.W. 2, N.I). Hot spring: 1. Area : Eur., As. Var. mimita Bleisch. Cl. & Gr. A. D. 96. V. H. Syn., Tab. LXIX, fig. 23. Laugarvaln (S.) A. F., Grimstadir (E.) B. P. Area: Eur., Grl., J. M.. Fz. J. Var. tenuirostris Grun. V. H. Trt. 402, Tab. XVII, fig. 556. 20 samples (S. 8, SAY. 2, N. 2, E. 7, s. 1. U Hot spring: 1. Nitzschia subtilis Grun. V. H. Trt. 401, Tab. XVII, fig. 552. Reykjavik (SAY.) H. Js., Thingvellir (SAY) E. W. & Ho. Area: Eur., Af., Am., Grl. Rhopalodia (). Muller. O. M. Afr. XI, 57. *Rhopalodia gibba (Ktz.) O. M. O. M. Rhop. 65. V. H. Trt., Tab. IX, figs. 352 a. b. (Epithemia g.). 216 samples (S. 48, S.W. 48, X.W. 3, N. 40, E. 73, s. 1. 4). Hot springs: 11. Area: Eur., Af., As., Am., Grl. FRESH-WATER DIATOMS FROM ICELAND 51 Rhopalodia gibberula (Ehr.) O. M. var. Van Hcnrcki forma a O. M. El. Kab. 292. V. H. Trt, Tab. IX, fig. 361 (Kpitb. gib. producta). 69 samples (S. 13, S.W. 22, N.W. 3, N. 15, E. 16). Hot springs: 13. Area: Eur., Af., As., Am. *Var. rnpestris (W. Sm.) O. M. O. M. El. Kab. 292. W. Sin. Syn., Tab. I, fig. 12 (Epitb. nip.). 50 samples (S. 7, S.W. 17, X.W. 2, X. 9, E. 15). Hot springs. Area: Eur., Af., Am. Rhopalodia gracilis O. M. O. M. Rhop. 63, Tab. II, fig. 6. 6 samples (S,W. 1, X. 3, E. 2). Area : Af. Rhopalodia parallela O. M. O. M. Rhop. 64. V. H. Trt., Tab. IX, fig. 353 (Epith. gib. parall.). 43 samples (S. 4, S.W. 12, X.W. 1, X. 7, E. 19). Hot springs: 5. Area: Eur., Af., As., Am. Rhopalodia uncinata O. M. O. M. Rhop. 63, Tab. II, figs. 3-4. Thingvallavatn (S.W.) C. H. O. Area : Af. Rhopalodia ventricosa O. M. O. M. Rhop. 64. V. H. Trt., Tab. IX, fig. 354 (Epith. vent.). 196 samples (S. 61, S.W. 38, X.W. 1, X. 32, E. 63, s. 1. 1 ). Hot springs. Area: Eur., Af., As., Am., Grl. Gonyraphideae Epithemia Breb. 1838. V. H. Trt. 394. *Epithemia Argus Ktz. V. H. Trt. 296, Tab. IX, fig. 355. 32 samples (S. 7, S.W. 12, X. 3, E. 8, s. 1. 2). Hot springs: 4. Area: Eur., Af, As., Am. Epithemia Hyndmanni W. Sm. V. H. Trt. 295, Tab. IX, fig. 350. 8 samples (S. 2, X. 3, E. 3). Area: Eur. Epithemia Sorex Kit. V. H. Trt. 295, Tab. IX, fig. 355. 40 samples (S. 15, S.W. 6, X. 10, E. 9). Area: Eur., Af., As., Grl. Var. amphicephala 0st. 0st. 0stg. Ferskv. 271, Tab. 1, fig. 9. 13 samples (S. 2, X. 2, E. 8, s. 1. 1). Hot spring: 1. Area: Grl. *Epithemla turgida (Ehr.) Klz. V. H. Trt. 294, Tab. IX, fig. 346 & 348 (E. t. granulata). 52 ERNST 0STRUP 139 samples (S. 35, S.W. 33. N.\Y. 2, N. 32, E. 33, s. 1. 4). Hot springs: 3. Area: Eur., Af., As., Am., Grl. Under Ep. turgida I include var. granulata, which can scarcely be kept apart from the typical species. Var. capitata Fricke. A. S. All., Tab. CCL, fig. 7. IlallormstaSir (E.) B. P. Area: Eur. Differs only from the type by having capitate apices. Forma anomala cnfr. 0st. D. D. 169, Tab V, fig. 110. Varma (S.) B. P., Skutustadir (N.) B. P., Lagarlljot (E.) B. P. This peculiar form which I, 1. c.. referring to Heiberg's Ep. globifera (cnfr. Heib. consp. 103, Tab. VI, fig. 22) placed as an abnormity of K. turgida. might be the sporangial form of this species. It has been found in 3 samples all containing plenty of E. turgida. : Epithemia Zebra (Ehr.) Ktz. V. H. Trt. 296, Tab. IX, fig. 357. 264 samples (S. 62, S.W. 63, X.W. 6, N. 41. E. 88, s. 1. 4), Hot springs: 15. Area: Eur., Af., As., Am. Var. longicornis M. Per. & Herib. Herib. Auv. 128, Tab. Ill, fig. 14. Laxa (S.) A. E., Vallanes (E.) II. Js., Hallormstadir (E.) B. P. Area: Eur. Var. longissima M. Per. & Herib. Herib. 1. c. 128, Tab. c., fig. 13. 8 samples (S.W. 5, E. 3). Hot spring: 1. Area : Eur. Var. i>robosddea Grun. V. H. Trt. 207, Tab. IX, fig. 358. 23 samples (S. 7. S.W. 2. N. 3. E. 11). Hot springs: 4. Area: Eur. Brachyraphideae Eunotia (Ehr.) 1837. Char, emend. II. Van Hcnivh. V. H. Trt. 2 ( J8. *Eunotia Arcus Ehr. V. H. Trl. 299, Tab. IX, fig. 362. 13 samples (S.I, S.W. 4, N. 4. E. I). Area: Eur., Af., As.. Am., (Irl., Spb. Var. bidens Grun. V. H. Tii. I. c.. Tab. c., fig. 305. 4 samples (S. 1, S.W. 2, E. 1). Area: Eur., Grl. Var. minor Grun. V. H. Tii. 1. c.. Tab. c., fig. 363. T> samples (S.W. 2, E. 3). Area: Eur., (irl. Var. lenella Grun. Schonf. Germ. 116. V. H. Syn., Tab. XXXIV. figs. 5 6. Thingvellir (S.W.) E. W. & Ho., Reykjavik (S.W.) II. Js. FRESH-WATER DIATOMS FROM ICELAND 53 Var. uncinata Grun. V. H. Trt. 299, Tab. IX, fig. 364. Alftatjorn (E.) B. P. Area: Eur. Eunotia bidentula W. Sm. V. H. Trt. 302, Tab. XXX, fig. 828. MosfellsheWi (S.W.) C. H. O., SeySisfjord (E.) B. P. Area: Eur. Eunotia diodon Ehr. V. H. Trt. 303, Tab. XXX, figs. 829-830. 8 samples (S.W. 3, NAY. 1, N. 1, E. 3). Area: Eur., Af., As., Am., Grl., Spb. Var. diminntd Grun. A. Cl. Lul. Lappni. 28. V. H. Syn., Tab. XXXIII, fig. 7. West Iceland St., Seydisfjord (E.) B. P. Eunotia elegans 0st. 0st. D. D. 172, Tab. V, fig. 10"). StaSastartur (S.W.) H. Js. Area: Eur. Eunotia exigua Breb. V. H. Trt. 300, Tab. IX, fig. 369. West Iceland St. Area: Eur., Am. Eunotia Faba (Ehr.) Grun. var. densestriata 0st. 0st. D. D. 173, Tab. V, fig. 107. Reykjavik (S.W.) C. H. O., Grimstadir (N.) B. P., Vallanes (E.) H. Js. Hot spring: 1. Area: Eur., Grl. Eunotia flexuosa Ktz. V. H. Trt. 304, Tab. IX, fig. 387. Ulfsbser (N.) B. P. Area: Eur. *Eunotia gracilis (Ehr.) Rbh. V. H. Trt. 300, Tab. IX, fig. 368. 48 samples (S.W. 25, N. 7, E. 16). Hot spring: 1. Area: Eur., Afr., Am, Grl, J. M., B. E, Spb., Fz. J. Eunotia impressa Ehr. var. angusta Grun. A. Cl. Lul. Lappm. 31. V. H. Syn., Tab. XXXV, fig. 1. 30 samples (S.W. 14, N.W. 3, N. 3, E. 10). Hot springs: 2. Area : Eur. Eunotia islandica sp. nov. Tab. nost. V, fig. 75. Long: 68/7, lat: !()//, str. 16 in 10 /*, subtiliter pnnctatis. Valva arcuata, margine dorsali bigibba. Apicibus recurvatis. Seydisfjord (E.) B. P. Not having been able to refer this form to any known species of Eunotia, I have thought it proper describing it as a new species. Eunotia lunaris (Ehr.)Grun. V. H. Trt. 303, Tab. IX, fig. 384. 94 samples (S. 4, S.W. 36, N.W. 3, N. 9, E. 41, s. 1. 1\ Hot springs: 2. Area: Eur, As, Am. 54 ERNST OSTRUP Var.? alpina Grim. De Ton. Syll. 808 (Psciuleun. alp.). V. H. Syn., Tab. XXXV, iig. 5. 4 samples, all S.W. Var. biliumris (Ehr.) Grun. V. H. Trt. 304, Tab. IX, fig. 386. HallormstaSr (E.) B. P. Area: Eur. Var. subarcnata (Naeg.) Grun. V. H. Trt. 1. c.. Tab. c., fig. 385. Minni Laxa (S.) A. E., West Iceland St. Eunotia major (W. Sm.) Rabh. V. H. Tit. 300, Tab. IX, fig. 366. 4 samples (S.W. 3, E.I). Hot spring: 1. Area: Eur., Grl. Var. bidens (Greg.) W. Sm. V. H. Trt. 1. c., Tab. c., fig. 367. Vallanes (E.) II. Js. Area: Eur. Eunotia Monodon Ehr. A. Cl. Lul. Lappm. 28. V. H. Syn., Tab. XXXIII, fig. 3. Etfar E.) II. J. Area: Eur., Grl. Eunotia Nymanniana Grun. A. Cl. Lul. Lappm. 33. V. H. Syn., Tab. XXXIV, fig. 8. 4 samples (S.W. 2, E. 2). Area: Eur., Am., Grl. Eunotia paludosa Grun. De Ton. Syll. 798. V. H. Syn., Tab. XXXIV, fig. 9. Ilusavik (N.) B. P., SkutustacMr (E.) B. P. Area: Eur. *Eunotia parallela Ehr. A. Cl. Lul. Lappm. 28. V. H. Syn., Tab. XXXIV, fig. 16. KetilstaiMr fSWJ H. Js., Omundarfjord (N.W.) B. P., Hof (N.) O. I). Area: Eur., As., Am., Grl., Spb., Fz. J. : - Eunotia pectinalis (Ktx.) Rbh. V. H. Trt. 300, Tab. IX, figs. 370 -371. 9 samples S.W. 5,. N.W. 1, E. 3). Area: Eur., Af., As., Am.. Grl. *Var. minor (Kt/.) Rbh. A. Cl. Lul. Lappm. 31. V. H. Syn., Tab. XXXIII, figs. 2021. 12 samples (S. 20, N.W. 2, N. 8, E. 12). Hot spring: 1. Area: Eur., Af., As., Am.. Grl., Kz. J. Var. stricta Rbh. A. C. 1. c. 31. V. H. Syn., Tab. c., fig. 18. 6 samples S. 1, S.W. 1, E. 4). Area: Eur. FRESH-WATER DIATOMS FROM ICELAND 55 Eunotia polyglyphis Grim. A. C. Lul. Lappm. 30. V. H. Syn., Tab. XXXIV, fig. 33. 4 samples (S. 1, S.W. 1, N.W. 1, E. 1). Hot spring. Area: Eur. Eunotia praerupta Ehr. V. H. Trl. 302., Tab. IX, fig. 376. 41 samples (S. 3, S.W. 10, N.W. 2, N. 17, E. 9). Hot springs: 3. Area: Eur., Grl. Var. bidens V. H. Trt. 302, Tab. IX, fig. 379. 16 samples (S. 6, S.W. 2, N.I, E. 7). Area: Eur., Grl., J. M., Fz. J. Var. bigibba Ktz. V. H. Trt. 1. c., Tab. c., fig. 380. V. H. Syn., Tab. XXXIV, fig. 27 (E. big. pumila). 6 samples (S. 1, S.W. 1, N. 2, E. 2). Area: Eur., Grl., Fz. J. Var. cnrta Grun. V. H. Trt. 1. c., Tab. c., fig. 377. 82 samples (S. 7, S.W. 41, N.W.I, N. 7, E. 26). Hot springs: 5. Area: Eur., Am., Grl., Fz. J. Var. laticeps Grun. A. Cl. Lul. Lappm. 34. V. H. Syn., Tab. XXXIV, fig. 25 (E. pr. lat. curta). Reykjanes (N.) K. Rsv., Eidar (E.) H. Js. Area: Eur., Grl., J. M., Fz. J. Eunotia robusta Ralfs var. Diadema Ralfs V. H. Trt. 303, Tab. IX, fig. 381, 1 st fig. 17 samples (S.W. 5, N. 2, E. 10). Hot spring: 1. Area: Eur., Am., Grl., Spb. Eunotia tridentula Ehr. var. perminuta Grun. A. Cl. Lul. Lappm. 28. V. H. Syn., Tab. XXXIV, fig. 30. Raudimalur (S.W.) A. F., West Iceland St., Eyjolfssta5ir (E.) H. Js. Area: Eur., Grl. Eunotia Triodon Ehr. V. H. Trt. 303, Tab. IX, fig. 383. 9 samples (S.I, SW. 5, N.I, E. 2). Hot spring: 1. Area : Eur., Am., Grl., Spb. *Eunotia Veneris Ktz. V. H. Trt. 301, Tab. XXX, fig. 826. Vik (S.) H. Js. Area : Eur. Var. obtushiscula Grun. V. H. Trt. 1. c., Tab. c,, fig. 387. Ketilsstadir (S.W.), H. Js. Area: Eur. 56 ERNST 0STRUP Arraphideae Ceratoneis Ehr. 1840. V. H. Trl. 305. *Ceratoneis Arcus Kt/. V. H. Trt. 306, Tab. X, fig. 401. 12G samples (S. 37, S.\V. 28. X.W.o. N. 15, E. 40, s. I. 1). Hot springs: 8. Area: Kur., Am., Grl., J. M., B. E., Spb.. Fx. J. Synedra Ehr. INIH. V. H. Trl. 307. *Synedra Acus (Ktz.) Grim. V. H. Trt. 311, Tab. X, fig. 420. Apavatn i.S." A. F., Sta6asta6ur (S. A. J-'., Laugaa SAY.) A. F. In a sample from Arnarsta[)i S.W. II. .Is. I have found a form analogous to Syn. Acus var. amphicephala H. L. Sm. V. H. Syn., Tab. XXXIX, fig. 8 (S. delicaliss. ami)hic. . *Var. delicatissima W. Sm. V. H. Trt. 312, Tab. X, fig. 421. 33 samples (S. 3, S.W. 5, X. 12, E. 13 . Area: Eur., As, Am. Var. mesoleja Grim. V. H. Syn., Tab. XXXIX, fig. 6 (Syn. delic. mesol.). 8 samples (S. 5, S.W. 2. X.I). Hot spring: 1. Area: Eur. Synedra amphicephala Ktz. V. H. Trt. 313, Tab. X, fig. 429. FroflarheiM (S.W.) H. Js. Area: Eur., Am. Var. austriaca Grim. De Ton. Syll. 660. V. H. Syn. XXXIX, figs. 16 a & b. Eystri Ranga (S.), Frodarheidi (S.W.) H. Js., Kolbeinsa N.W.) II. Js. Area: Eur. Synedra capitata Ehr. V. H.Trt. 313, Tab. X, fig. 427. 17 samples (S. 2, S.W. 3, X. 4, E. 8). Hot spring: 1. Area: Eur., As. Synedra famelica Klz. var. minuscula Grim. De Ton. Syll. 660. V. H. Syn., Tab. XXXIX, fig. 13. 5 samples (S. 2, S.W. 2, E. 1). Area: Eur. Synedra familiaris Kt/. forma major. De Ton. Syll. 667. V. H. Syn., Tab. XL, fig. 16. Ketilstaftir S.W. H. Js., Skutusta&ir (X.) B. P. Area: Eur. Synedra pulchella Kt/. V. H. Trt. 301), Tab. X, fig. 402. 22 samples S.I. S.W. 15, N. 4, E. 2). Hot spring: 1. Area: Kur., Af., As., Am., Grl. FRESH-WATER DIATOMS FROM ICKLAND 57 Var. naviculacea Grun. De Ton. Syll. 652. V. H. Syn., Tab. XLI, fig. 8. Grimsey (N.) O. D. Area: Eur. Synedra radians (Ktz.) Grun. V. H. Trt. 312, Tab. X, fig. 423. 7 samples (S. 3, S.W. 4, E. 1). Area: Eur., As., Grl. Synedra rostrata Pant. Pant. Bal. S. 76, Tab. VIII, fig. 4. 12 samples (S. 2, S.W. 4, N. 7). Hot spring: 1. Area: Eur. Hustedt claims in Sud. p. 46, that Syn. rostrata is to be considered a sporangial form "a us dem Gebiet der Synedra Ulna". Synedra rumpens Ktz. var.? fragilaroides Grun. cnt'r. De Ton. 680. V. Syn., Tab. XL, fig. 12. 38 samples (S. 14, S.W. 14, N.W. 1, N. 4, E. 4, s. 1. 1). Hot springs: 3. Area: Eur., Am. Var. islandica var. nov., Tab. nost. V, fig. 76. Long: 36 /<, lat: 3,2 , sir. 20 in 10 /<. Valva linear!, apices versus leniter attenuata. Striis media in parte valvae aream nudam relinquentibus. Hallormstadr (E.) B. P. I have placed this small Synedra as a variant of S. rumpens, pos- sibly to be placed nearest to S. rump, genuina (V. H. Syn., Tab. XL, fig. 14), owing to its close slriation; for the same reason perhaps related to S. (Vaucherise var.?) capitellata Grun. (V. H. Syn., Tab. XL, fig. 26). *Synedra Ulna (Nitzsch) Ehr. V. H. Trt. 310, Tab. X, fig. 409". 207 samples (S. 50, S.W. 50, N.W. 6, N. 32, E. 69). Hot springs: 11 Area: Eur., Af., As., Am., Grl. Var. amphirlujnchns Ehr. V. H. Trt. 311, Tab. X, fig. 414. Minni Laxa (S.) A. F. Area: Eur. Var. Danica Ktz. V. H. Trt. 1. c., Tab. c., fig. 415. 148 samples (S. 33, S.W. 30, N. 18, E. 67). Hot springs: 7. Area : Eur., Af., Grl., B. E. In 60 samples (S. 12, S.W. 16, N.W.I, N. 2, E. 25, s. 1. 4) and in 2 hot springs I have noted S. Ulna, which however could not be deter- mined accurately, they being only present as fragments or lying on the connecting zone. Var. longissima W. Sm. V. H. Trt. 310, Tab. c., fig. 412. Laugaa (S.) A. F., Krokur (S.) H. Js., Hornarfjordr i E.) St. Area: Eur., Af. 58 ERNST 0STRUP Forma arcuata Tab. nost. V, fig. 77 (X 333). Long, chordae arcus 302,4 u, lat: sagittae arcus 64,5 a, str. 11 in 10 n. Valva arcuata, in niedio leniter inflata. I Ihink this form can only be considered as a curved form of S. Ulna longissima. Asterionella Hassall 1850. V. H. Trt. 320. *Asterionella formosa Hass. var. gracillima (Hantzsch) Grun. V. H. Trt. 321, Tab. XI, fig. 440. 8 samples, all S.W. Area: Ubiquist, Grl. Fragilaria Lyngbye 1819. V. H. Trt. 323. Fragilaria Baculus sp. nov., Tab. nost. V, fig. 78. Long: 24/i, lat: 3,2 /<, str. 12,5 in 10 //. Valva linear!, apicibus rotundatis. Area apicali angustissima. Striis parallelis. Egilstadir (E.) B. P. *Fragilaria capucina Desmz. V. H. Trt. 325, Tab. XI, fig. 446. SkeiSararsandur (S.) St., Krokur (S.) H. Js. Area: Eur., At'., As., Am., Grl., Spb., Fz. J. Var. acuminata Grun. V. H. Trt. 1. c,, Tab. c,, fig. 449. Steinsmyri (S.) H. Js. Area: Eur., As., Am. Var. aciita Grun. V. H. Trt. 1. c., Tab. c., fig. 448. 9 samples ;S. 7, S.W. 2). Var. lanci'olata Grun. Hust. Sud. 38. V. H. Syn, Tab. XLV, fig. 5. Thjorsa (S.) A. F. Area: Eur., Am. *Var. mesolepta Hhh. V. H. Trt. 325, Tab. XI, fig. 447. Skeidardrsandur S.) St. Area: Eur. ^Fragilaria construens (Ehr.) Grun. V. H. Trt. 325, Tab. XL fig. 450. 52 samples (S. 16, S.W. 19, N. 7, E. 10). Hot spring: I. Area : Eur., Af., As., Am., Grl., B. E. Var. binodis. V. H. Trl. 32(3, Tab. c., fig. 452. 14 samples (S. 6. S.W. 5, N.W.I, E. 2). Area: Eur., At'., Am. FRESH-WATER DIATOMS FROM ICELAND 59 Var. /;n/ni7a Grun. V. H. Syn., Tab. XLV, fig. 21 a. Kirkjubccr (S.) H. Js. Area: Eur., As. Var. semibinodis 0st. 0st. D. D. 190, Tab. V, fig. 115. Laxa (S.) A. F. Area : Eur. Var. Venter Grun. V. H. Trt. 325, Tab. XI, fig. 451. 53 samples (S. 11, S.W. 14, N. 11. E. 17). Area: Eur., Af.. Am., Grl. *Fragilaria crotonensis (A. M. Edwards) Kitton. V. H. Trt. 324, Tab. XI, fig. 444. 10 samples (S.W. 1, N. 1, E. 8). Area: Eur. Fragilaria intermedia Grun. V. H. Trt. 32(5 (F. tenuicollis Heib. interm.). V. H. Syn., Tab. XLV, figs. 911. 85 samples (S. 42, S.W. 25, N. 5, E. 10, s. 1. 31 Hot springs: 2. Area : Eur., As., Grl. Fragilaria lapponica Grun. A. C. Lul. Lappm. V. H. Syn., Tab. XLV, fig. 35. Ulfjolsvatn (S.) A. F., Apavatn (S.) A. F. Area: Eur., Grl. Fragilaria mutabilis (W. Sm.) Grun. V. H. Trt. 326, Tab. XI, fig. 454. 39 samples (S. 11, S.W. 4, N. 6, E. 17, s. 1. 1). Hot spring: 1. Area: Eur., Af., As., Am., Grl. Var. elliptica Schum. f. minor. Meist. S. 66 (Fr. ellipt). V. H. Syn., Tab. XLV, figs. 1617. 16 samples (S. 6, S.W. 6, E. 4). Area: Eur., As., Am. Var. inflata var. nov., Tab. nost. V, fig. 79. Long: 36 /<, lat: 6,4 //, str. 8,5 in 10 in. Valva lineari, in medio inflata, apicibus rotundatis. Striis pa- rallelis, aream apicalem satis latam relinquentibus. Hallormstadr (E.) B. P. *Var. intcrcedens Grun. V. H. Syn., Tab. XLV, fig. 13. 9 samples (S. 5, S,W. 1, N.W. 1, E. 2). Hot spring: 1. Area : Eur., As. Var. minutissimq Grun. V. H. Syn., Tab. c.. fig. 14. Skeidararsandur (S.) St., Myvatn (N.) Rd. Area: Eur., Am. Fragilaria parasitica W. Sm. W. Sm. Syn. II, 19, Tab. LX, fig. 375. 8 samples (S. 3 ; S.W. 3, N. 1, E. 1). Area: Eur., Af., As. 60 ERNST 0STRIP Fragilaria producta Lgst. Lgst. Spb. If), Tab. I, fig. 1 (F. aequalis prod.). 41 samples (S. (5, S.W. 12, N.W. 2, X. 8, F. U . Area: B. E., Spb. Fragilaria rhombica sp. nov., Tab. nost. V, lig. 80. Long: !(')//, Int: In, sir. 10 in 10 n. Valva rhomboidea, apices subcapitatos versus valde altenuata. Striis medium partcm valvne versus obliteranlibus ibi(|ue areolam centralem relinqventibus. Grimscy (X.) O. I). I think this small Fragilaria is probably to be considered as an intermediate form between F. constr. venter and F. Ilarrisoni. Fragilaria Smithiana Grun. V. H. Syn., Tab. XLV, lig. 1. Ulfjulsvaln S.) A. F. Area: Eur. Fragilaria triundulata sp. nov., Tab. nost. V, fig. 81. Long: 2C. 11, lat: 6,7 /<, sir. !(>,(> in 10 //. Valva leniter triundulala, apicibus capitalis. Striis marginalibus, aream aj)icalem lalain relinquentibus. Apavatn S.) B. P. This form has nothing to do with Fr. construens var. triundulata Reicbelt (en IV. Osl. Dint. Ail. 57, Tab. II, lig. 15). Possibly it is more closely related to Frag, trigibba Pant. (Pant. Hal. S. 79, Tab. IX, fig. 224 , but it is scarcely identical with it. Fragilaria undata W. Sin. V. H. Trt. 324. A. S. All., Tab. CCXC, ligs. 48-(H. 5 samples (S.W. 2. X. 1, E. 2). Area: Fur., Grl. In tab. nostr.. lig. S2, I have given a figure of a particularly elegantly built form of Frag, undata. It was found in a sample from West Ice- land. SI *Fragilaria virescens Kalis. V. H. Trt. 323, Tab. XI, lig. 442. ::() samples S. 5, S.W. 15, X.W.I, X. 5, E. 15, s. 1. 1). Area: Fur., At'., As., Am., Grl. Var.? (>.ri !f ua Grim. V. H. Syn., Tab. XLIV, ligs. 2 3. (i samples S. 2. X. 2, K.I, s. 1. 1). Hot spring: 1. Area: Fur. Meridion Agardb 1847. V. H. Trt. 347. :i: Meridion circulare Ag. V. H. Trl. 347, Tab. XI, (ig. 474. 15 17 samples (S. 111). S.W. 71, X.W. 15, X. 40. F. 157, s. 1. 4). Hot springs: 12. Area: Fur., A I'., As., Am., Grl. FRESH-WATER DIATOMS FROM ICELAND 61 Forma anormalis, cnfr. A. S. All., Tab. CCLXVII, figs. 3740, which figures F. Fricke thinks can be understood thus: fig. 37, "vielleicht Auxo- spore"; figs. 38 39, "vielleichl teratologische Auxosporen" ; fig. 40, "viel- leicht die Zelle zweiter oder folgender Generation". 10 samples (S.I, S.W. 3, E. 6). In these samples varying in dif- ferent ways. Diatoma de Candolle 1805. V. H. Trt. 348. *Diatoma hiemale (Lyngbye) Heib. V. H. Trt. 350. A. S. Atl., Tab. CCLXVII, figs. 1633 (Dial. hiem. mesodon). 258 samples (S. 57, S.W. 64, N.W. 11, N. 33, E. 91, s. 1. 2). Hot springs: 10. Area : Eur., As., Am., Grl. The reason, why I place this form as a Dial, hiemale, and in ad- dition cite figures of D. hiemale, is, that I consider Heiberg (Consp. D. 58) is right when he says ''it is perfectly clear that it (o : var. mesodon) is only a short form of Diatoma hiemale", and that ''specimens of both forms are by Lyngbye determined as Fragilaria (now Diatoma) hiemale". It is especially the short form met with in Icelandic material. Diatoma elongatum Ag. V. H. Trt. 349, Tab. XI, fig. 467. Ulfjolsvatn (S.) A. F., Reykjavik (S.W.) H. Js., HallormstaSr (E.) B. P. Area: Eur., Af., As., Am., Grl. Var. minus Grun. A. S. Atl., Tab. CCLXVIII, figs. 60 61. Krossa (S.) H. Js., Stykkisholmur (S.W) H. Js. Area: Eur., Am. Var. tenue Ag. V. H. Trait. 349, Tab. XI, fig. 468. 35 samples (S. 10, S.W. 15, N.W. 1, N. 2, E. 6, s. 1. 1). Hot spring: 1. Area: Eur., Am., Spb., Fz. J. *Diatoma vulgare Bory. V. H. Trt. 348, Tab. XI, fig. 465. 43 samples (S. 12, S.W. 12, N.W. 2, N. 7, E. 10). Area: Eur., Af., As., Am., Grl., Fz. J. Denticula Ktz. 1844. V. H. Trt. 351. *Denticula elegans Ktz. V. H. Trt. 351, Tab. XXXI, fig. 860. 10 samples (S.I, S.W. 3, N. 5, E.I). Hot spring: 1 Area : Eur., Am. Denticula islandica sp. nov., Tab. nost. V, fig. 83. Long: 40 //, lat: 4 //, costis 6,25 in 10 //. Valva lineari , apicibus subacutis. Costis seriebus punctorum subtilissimorum interpositis. Vallanes (E.) B. P. Possibly this form is nearest related to Dent, subtilis Grun. (V. H. Syn., Tab. XLIX, figs. 10 13), although it differs from this, especially in 62 ERNST 0STRI/1' size, or it is perhaps related to Dent, lauta Hail. (V. H. Syn., Tab. XLIX, figs. 12), but it is hardly identical with either of these. Denticula subtilis Grun. V. H. Trt. 352, Tab. XI, fig. 4(54. 5 samples (SAY. 2, E. 3). Area: Eur., Af., As., Am. Denticula tenuis Ktz. V. H. Trt. 352, Tab. XI, fig. 461. 5 samples :S.W. 3, E. 2). Area: Eur.. Af., As., Am. Diatomella Greville 1855. V. H. Trl. 35;}. *Diatomella Balfouriana Grev. V. H. Trt. 353, fig. 104. 168 samples (S. 20, S.W. 55. NAY. 5, X. 34, E. 5 4 . Hot springs: 7. Area: Ear., Am., Grl., B. E., Spb., Fz. J. Tabellaria Ehr. 1839. V. H. Trt. 356. *Tabellaria fenestrata (Lyngb.) Ktz. V. H. Trt. 356, Tab. XI, fig. 477. 108 samples (S. 17, SAY. 39, NAY. 2, N. 7, E. 43). Hot springs: 2. Area: Eur., At'., As., Am., Grl. *Tabellaria flocculosa (Roth) Kl/. V. H. Trt. 357, Tab. XI, fig. 478. 192 samples (S. 36. S.W. 60, N. W. 6, N. 28, E. 60, s. 1. 2 . Hot springs: 10. Area: Eur., Af., As., Am., Grl., J. M., B. E., Spb., Fz. J. Tetracyclus (Raffs) Grun. 1862. V. H. Trt. o57. Tetracyclus emarginatus W. Sm. W. Sin. Syn. II, 38. Herib. Auv., Tab. Ill, fig. 27. 30 samples ;S. 4, SAY. 14, N. 5, E. 7). Area: Eur. FRESH-WATER DIATOMS FROM ICELAND 63 CENTRIC^E Rhizosolenia (Ehr., Brightw.) H. Perag. emend. 1892. *Rhizosolenia eriense H. L. Smith. Ostenf. Thingv. 1123, Tab. II, figs. 13. Thingvallavatn (SAY.) C. H. O. Area: Ear., Am. Found by C. H. Ostenfeld, not by myself. *Rhizosolenia paludosa O. Zacharias. Ostenf. Thingv. 1124, Tab. II, figs. 4-5. Thingvallavatn (S.W.) C. H. O. Area: Eur. Found by C. H. Ostenfeld, not by myself. Melosira Ag. 1824. V. H. Trt. 438. Melosira ambigua O. M. O. M. Nyas. 283, Tab. IV, figs. 910. Minni Laxa (S.) A. F., Seydisfjardarheidi (E.) H. Js., Eyjolfstadir (E.) H. Js. Area: Eur., Af., As. *Melosira arenaria Moore. V. H. Trt. 443, Tab. XIX, fig. 621. Thingvallavatn (S W.) C. H. O. Area: Eur., As. Found by O. H. Ostenfeld (cnfr. Ostf. Thingv. 1 115), not by myself. *Melosira crenulata Ehr. O. M. Nyas. 263. V. H. Trt., Tab. XIX, fig. 618. 27 samples (S. 9. SAY. 2, N. 5, E. 11). Area: Eur., Af., As., Am. *Melosira distans (Ehr.) Ralfs var. alpigena Grun. O. M. Nyas. 271. V. H. Syn. LXXXVI, figs. 2829. 55 samples (S. 4, S\Y. 13, NAY. 5, N. 4, E. 29). Area: Eur. Var. nivalis (W. Sm.) Grun. O. M. Nyas. 272. V. H. Syn., Tab. c.,. figs. 2527. 21 samples SAY. 6, NAY. 2, N. 7, E. 6). Hot spring: 1. Area: Eur., Grl. *MeIosira granulata (Ehr.) Ralfs. O. M. Nyas. 267. O. M. Mut., Tab. XVII, figs. 9-10. 7 samples (S. 1, SAY. 4, N. 1, E. 1). Area : Eur., Af., As., Am , Grl., Fz. J. 64 ERNST 0STRUP :i: Me!osira islandica (). M. (). M. Pleom. 56, Tab. I, figs. 13. 1 1 samples (S.\V. 9, E. 2). Area: Iceland. *Melosira italica Ktz. vnr. tennis (Ktz.) O. M. O. M. Nyas. 265. V. H.Syn., Tab. LXXXVIII, figs. 9 a, 10, 13, 14 (13-14 M. crenulata ambigua). 123 samples (S. 22, S.W. 22. X.W.I. N. 22, E. 56). Hot springs: 2. Area: Eur.. Af., Am., Grl. *Var. temiissima (Grim.) O. M. O. M. Nyas. 205. V. H. Syn., Tab. c., fig. 11 & 16 (16 M. Binderiana). 20 samples (S. 3, S.W. 11, N. 3, E. 3). Area: Eur., Af. Melosira laevis (Ehr.) Grun. O. M. Nyas. 265. A. S. All., Tab. CLXXXI, fig. 84. 6 samples (S. 1. S.W. 2, E. 3). Area: Eur., B. E. *Melosira Roeseana Rabh. V. H. Trl. 442, Tab. XIX, fig. 614. 11 samples S. 3, S.W.I, N. 2, E. 5 . Area: Eur., Far., Grl., J. M., Spb. Melosira Stefanssoni sp. nov., Tab. nost. V, fig. 84. Diam. 914 u. Disco piano, margine serie manifesta granularum praedita. In- leriori parte disci granulis satis magnis, centro-punctatis el irregu- lariter distributis, repleta. S. 1. (West-Iceland) St. This Melosira is perhaps related to fig. 41 in A. S. All., Tab. CLXXXI, but it lacks the inner ring on the discus. That form of A. S. is from the Pitt River .Oregon) and is according to Grove M. distans var. scalaris Grun.. while Cleve lakes it to be a variety of Mel. crenulata. 'Melosira Varennarum M. Per. & Herib. Herib. Dial. d'Auv. 189, Tab. V, figs. 12-14. 6 samples (S.W. 5, E. 1). Area: Eur. Melosira varians Ag. V. H. Trl. 441, Tab. XVIII, fig. 611. 113 samples (S. 48, S.W. 22. X.W. 2, N. 23, E. 17, s. 1. 1). Hoi springs: 1. Area: Eur., Af., As., Am., Grl. Cyclotella Ktz. 1833. V. H Trt. 445. Cyclotella antiqua W. Sm. V. H. Trl. 446, Tab. XXII, fig. 652. 18 samples iS. 3, S.W. 4, N. 1, E. 10). Area: Eur., As., Grl., Spb. FRKSII-WATKK DIATOMS KKOM ICELAND 65 Cyclotella comta (Klir.) Klz. V. H. Trt. 446, Tab. XXII, fig. 653. Ostenf. Thingv. 1115, Tab. I, ligs. 910. Thingvallavatn f.S.W.) C. H. O. Area: Eur., Ai'., As. Found by C. II. Ostenfeld. not by myself. Cyclotella Kutzingiana Chauvin. V. H. Trt. 447, Tab. XXII, fig. 657. 18 samples (S. 1, SW. 3, N. 1. K. 13). Area: Eur., Af, As. Cyclotella Meneghiniana Ktz. V. H. Trt. 447, Tab. XXII, fig. 656. 6 samples (S.W. 5, E. 1). Area: Eur., Af., As., Am. Stephanodiscus (Khr. 1845) Grim, emend. 1880. Stephanodiscus Astraea (Khr.) Grun. Cl. & Gr. A. D. 114. V. H. Syn., Tab. XCV, fig. 5. Krisuvik (S.) C. H. O. Area: Eur., Af., As., Grl., Fz. J. The following are forms of fresh -water Diatoms (including a few forms from brackish water) not found again by me, but by other Diatomologists, without their having definitely localised them. Ceratoneis Arcus (Ehr.) Kiitz. var. ainphio.vys Rabh. Rabh. Siissw. 37, Tab. IX, fig. 4. Found by Relloc. Cyclotella minutissima. Unknown to me. Perhaps identic with Cyclotella minutula Ktz. = Stephanodiscus Astraea (Khr.) Grun. var. minutulus (Ktz.) Grun. V. H. Syn. CXCV, figs. 78 or with Cyclo- tella operculata (Ag.) Kiitz. var. minutula (Ktz.) Br. Brim Diat. Alp. & Jura 133, Tab. I, fig. 7. F. b. K. Belloc. Cymbella norvegica Grun. Cl. Syn. I, 169. A. S. Atl., Tab. X, fig. 41. F. b. P. T. Cleve. This Cymbella is very closely related to C. gracilis Rabh. (cnfr. Cl: 1. c.) and is hardly a different species. Denticula obtusa W. Sm. W. Sm. Syn. II, 19, Tab. XXXIV, fig. 292. F. b. K. Belloc, This species is without doubt identical with Nit/.schia Denticula Grun. Gomphonema geminatum Lyngb. Cl. Syn. I, 186. V. H. Trt., Tab. XXIX, fig. 10. F. b. K. Belloc. The Botany of Iceland. Vol. II. 5 66 ERNST 0STRUP: FRESH-WATER DIATOMS FROM ICELAND Mastogloia Brauni (irun. Cl. Syn. II, 15.S. V. II. Trt., Tab. II, fig. 66. F. h. E. Belloc. Mastogloia Smithi Tbwaites v. lanceolala Grun. ('A. Syn. II, 152. Pant. loss. I'ng. III. Tab. XXXV, tig. 520. F. h. K. Belloc. Navicula binodis Ehr. Cl. Syn. I, 129. V. H. Trt., Tab. V, lig. 2M5. F. b. E. Belloc. Navicula scutelloides W. Sin. Cl. Syn. II, 40. V. H. Trt., Tab. XXVII, iig. TIM. F. b. C. Hansen. Neidium amphigomphus Ehr. Cl. Syn. I, 69. V. H. Trt.. Tab. V, fig. 218 (Nav. Iridis amphig.). F. b. E. Belloc. Nitzschia acicularis W. Sm. V. H. Trt. 405, Tab. XVII, lig. 571. F. b. E. Belloc. Nitzschia communis Uabh. V. H. Trt. 402, Tab. XVII, fig. 560. F. b. E. Bclloc. Nitzschia obtusa W. Sin. V. H. Trt. 397, Tab. XVI. fig. 537. F. b. E. Belloc. Nitzschia parvula W. Sm. W. Sm. Syn. I, 41, Tab. XIII, fig. 106. F. b. E. Belloc. Nitzschia Sigma W. Sm. v. Sigmatella (irun. V. H. Trt. 397, Tab. XVI, fig. 535. F. b. E. Belloc. TABULAR SURVEY EHNST 0STHUP: FRESH- WATER DIATOMS FROM ICELAND 69 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 Achnanthes affinis Universal distribution Distribution in the different parts of Iceland Eur. Af. As. Am. Aust Grl. J.M. B.E. Spli. Fz.J S. S.W.M.W N. E. 8.1. X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X . X X X X X X X X X X X X X - - X X X X X X X X X X X X X X X X X X X X X X X X X X X . X X > .X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X Biasolettiana Calcar coarctata delicatula exigua exilis lanceolata capitata dubia elliptica faeroensis linearis minutissima Peragalli rhvncocenhala .. tylophora Amphipleura pellucida Amphora cimbrica coffaeiformis Normani ovalis Pediculus perpusilla protracta gallica veneta Anomoeoneis brachysira .... exilis sculpta sphserophora . . . zellensis Asterionella formosa gracill Caloneis alpestris amnhisbaena . 70 ERNST 0STRUP 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 6(1 61 62 63 (54 65 66 67 bacillaris Universal distribution Distribution in the different parts of Iceland nr. Af. As. Am. lihl. l,rl. J.M. II. L S|.l,. 1/..I. S. S.W. \.\V. N. E. |i.l. X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X y. X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X f. X X X X X X X X X X X X X X X X X X X X X X X X X X . X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X bodonensis Clevei . fasciata ladogensis . . ohtusa . Silicula scnuina biconstricta inflata subventricosa ventricosa Campylodiscus hibernicus noricus Ceratoneis Arcus Cocconeis llexella intermedia ininuta alpestris I'lacentula Cyclotella anticiua comta Kiitzingiana Menegbiniana Cymatopleura elliptica Solea ... Cymbella ,n| ii;il is affinis amphicephala an^ustata aspera dubravic Ceratii Cistula . FRESH-WATER DIATOMS FROM ICELAND 71 68 69 70 71 72 73 74 75 76 77 85 86 87 88 89 9(1 91 92 93 94 99 100 101 102 103 Cist u la arctica . . . Caldogast. maculata . cuspidata cy in hi form is Khrcnbergi delecta gracilis helvetica heteroplcura min. 78 incerta navic. 79 lanceolata.. 80 I cornuta 81 ventricosa 82 lapponica 83 microcephala 84 naviculiformis parva prostrata sinuata stauroneiformis.. turgida ventricosa.. Denticula elegans subtilis tennis . Diatoma hiemale.. 95 elongatum. 96 97 98 minus ten ne . vulgare Diatomella Balfouriana Diploneis Boldtiana robusta . . . elliptica ovalis . Universal distribution Distribution in the different parts of Iceland Eur. A'. As. Am. liM. l.rl. i! J.M. B.E. Spb. F/.J S. s.tt. N.\\. N. B. S.I. X X X X X X X X X X X X - X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X /, X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X y. X X X X X .-. X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X < X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X x: X X X X X X X X X X X X 72 ERNST 0STRI 1> 104 [05 10f> 107 108 109 110 111 112 113 114 115 116 117 us 11!) 120 121 122 123 124 125 126 127 12S 129 130 131 i:r_> 133 1154 135 136 137 138 139 141) 141 142 14:< ovalis oblongella Universal distribution Distribution in the di tit-rent parts of Iceland hir. Af. \s. Am. \us . lirl. J.M. U.K. >|il. I'/.J. S. S.\\. \.\\. N. K. 1.1. X X /. X X y. X X X X X X X X X X X X X X X X X X X X X X X X X X X X x X X X X X X X X X" X X X X X X X X X X X X X X X X X X X X X X X X X X X i X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X puinila Puella subovalis Epithemia Arijiis . Hvndmanni Sorex amphicepli turgida anom capitata Zebra longicornis longissima proboscidea . Eunotia Arcus bidens minor tenella uncinata bidentula .... . . Diodon d i m i n u t a elegans cxigua . Faba densestr flexuosa gracilis ini|)ressa ang lunaris alpina l>i lunaris subarcuata major bidens . . Monodon Nymanniana paludosa . . parallela nectinalis . FRESH-WATER DIATOMS FROM ICELAND 144 145 146 147 14S 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 pectinalis minor Universal distribution Distribution in the different parts of Iceland Eur. Af. U. Im. \l|v|. Grl. J.M. B.t, Spli. I/..I. S. S.\\. \\V. N. E. S.I. X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X ?< X. X X X X X X - X X X X X X X X X X X X X x X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X stricta Dolvfflvnliis prserupta bidens bigibba curta . . laticeps robusta Diad tridentula permin Triodon . . Veneris obtusiusc Fragilaria capucina acuminata acuta lanceolata mesolepta construens binodis pumila semibin venter crotonensis intermedia. lapponica mutabilis elliptica intercedens minutiss parasitica producta . . Smithiana undata virescens exigua Frustulia rhomboides saxon leptoceph vulgaris 74 ERNST 0STHUP 1 83 184 185 186 187 188 189 190 191 192 193 194 195 198 199 200 201 202 203 204 205 206 207 208 20! I 210 211 212 213 214 215 216 217 218 210 220 Gomphonema acuminatum coronatum . . . . elongatum pusilla trigonocephala. angustatum prod gracile aurit dicliot navicul intricatum dichotom Vibrio Lagerheimi lanceolatum insigne olivaceum calcareum stauroneif. parvulum Salinarutn subclavatum montanum. . . . Mustcla subtile . . Gyrosigma acuminatum attenuatum . Hantzschia amphioxys constricta . elongata . . dubravicensis virgata leptoc Mastogloia elliptica Dansei Grevillei Smitbi lacust. . Melosira ambigua arcnaria crcnulata distans alpig nivalis.. I niversal distribution Distribution in tbe different parts of Iceland Kur. Af. As. Am. lu.! S.VL V L. i.l. X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X FRESH-WATER DIATOMS FHOM ICELAND 77 303 304 305 30(> 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 32G 327 328 329 3.30 3:n 332 333 334 335 33(i 337 338 339 340 341 342 343 dilatatum Universal distribution Distribution in the different parts of Iceland Lur. If. As. \m. I IN. lirl. .I.H. B.E. Spb. F/ 1 s. s.\\. \ \\ 1. L. i.l. X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X . X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X ' X X X X X X X X X X X X X X X X x- X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X 1 dubium fasciatum . . ... Hitchcockii incurva . . . Iridis productum Nitzschia amphibia acutiusc Frauenf. angustata apiculata . commutata debilis Denticula dissipata Frustulum Hantzschiana glacial Heutleriana intermedia Kittli Kutzingiana linearis Nathorsti Palea fonticola minuta .... tenuirost serians Sigma . Clausi sigmoidea sinuata staijnoruni tliermalis minor . subtilis Trvblion. Viet vitrea recta salin Oestrupi 78 ERNST 0STHI'!' 344 345 346 347 348 349 350 351 352 353 354 355 356 :C)7 358 359 360 361 :w> 363 364 365 366 367 368 : 370 371 372 373 374 37.-) 37i .'577 378 37! 380 381 382 383 384 385 Pinnularia acrosphseria aestuarii alpina appendiculata budensis.. . Balfouriana borealis brevicost liuearis.. Brauni Brebissoni diminuta linearis brevicostata leptostauron . Dactylus distinguenda divergens ellipt elongata divergentissima tlexuosa gracillima hemiptera interrupta intermedia interrupta stauroneif. . . . biceps icostauron karelica lata - minor Legumen Icptosoma major linearis mesogongyla interrupta. mesolepta angusta pol yonca stauroneif. . . microstauron molaris Universal distribution Distribution in the different parts of Iceland Bar. Af. As. Am. lust. drl. J.M. B.L Spb. F/.J. s. s.w. O. N. t. s.l. x X i X X X X X X i X X X xxx X x II x X X X X x X X X X x x - X X X X X x : x X x II x X X X X X X X X X X X X X X X x ; x X X X x. i x X X X X X X X X X X X X x x X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X x x X X X X X X X X X X X X X X X X X X X xxx X X X X X X X X X X X X X X X X X X X X X X X X X X X X x xxx X X X X X x x X X X X X X X X X X X X X X X X X x x X X X X X X X X X X X X X X X X X X X X X X X X X X X - X X X X X X X X X X X ' X X X X X X X X X X X X X X X X X X X X X X X X X X FRESH-WATEH DIATOMS FROM ICELAND 79 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 nodosa Universal distribution Distribution in the different parts of Iceland Eur. Af. As. Am. Aust/Grl. J.H. B.E. Spb. h,\. S. S.W. \.W. N. E. s.l. X X X X X - X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X Oculus parallela crassa parva Lasjerst. . Paulensis platvceph secernenda stauroptera interr. stomatoph streptoraphe minor subcapitata paucistr sublinearis subsolaris viridis commut fallax intermedia leptogong. . rupestris Rhizosolenia eriensis paludosa Rhoicosphenla curvata Rhopalodia gibba . . gibberula rupestris gracilis parallela . uncinata ventricosa. . . . Stauroneis acuta anceps birostris . . so ERNST 0STRIP 423 424 425 426 427 428 429 430 431 432 433 43G 437 4 as 439 440 441 442 4415 444 14.') 44<; 447 448 ll'.i 450 451 152 453 I.', I 455 45(1 457 458 anceps gracilis hyalina lincaris siberica. . . . javanica , Legumen obtusa. ... pa rv ul a prod , Phoenicentefon amphil. Smithi . . Stenopterobia 434 intermedia Stephanodiscus 435 Astra-a Surirella biseriata Engleri ang linearis constricta. . . Molk'riana ovalis angusta minuta ovata pandurif. . pinnata robusta splcudida . . . turgida Synedra Acus delicatiss mesoleja ampbicepli austriaca , capitata famelica minusc. . . . , Camiliaris major . . . . puldidla navifiil. . Universal distribution Distribution in tbe dilferent parts of Iceland Lur. Af. As. Am. Ansl. Grl. .1.11. RE. Spb. \'i.L S. SJ. \.\V. V B. 1.1. X X XX X X - X X X X X X X X X X X X X X X X X X X X X X X X X X X X X y X X y X X X X X X X X X X X X X X X X X X X X X X X X v X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X x X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X y X X X X X X X X X X X . X X X 5^ X X X X X X X X X X X X X X X X X X X X FRESH-WATER DIATOMS FROM ICELAND 81 459 460 461 4(52 463 464 465 466 467 468 radians Universal distribution Distribution in the different parts of Iceland Eur. U. k tin. lust. (irl. J.M. H.E. S|i1i. F/...I. S. S.\V. N.W. N. L. s. 1. X X X X X X X X - X X X X X X X X X X X X X 251 54 X X X X X X X X X X X X y X X X X y 299 64 y. y. X X X X X X X X X X X X X X X X X X X X X X X X X 71 15 rostrata rurnpcns frag Ulna amphir danica longiss Tabellaria fenestrata flocculosa Tetracyclus emarginatus Total . . . % 44.") 1)5 184 39 223 48 104 22 192 41 49 10 54 12 69 15 76 16 332 71 104 22 240 51 328 70 From this it appears that the distribution is very similar to that of the rest of Europe, as 95 /o of the Icelandic forms also occur there; next come Asia and America with about 50 %. As for the Arctic regions, Greenland stands highest with 41 ,o. In Iceland the number of species is greatest and almost the same in S W. and E., about 70 o; from these parts the greatest number of samples originate, viz. 148 and 191 respectively. The Botany of Iceland Vol. II. 82 KHNST OSTRl'I' Forms found in 100 samples or more. y. ._ '~i ~~ 'Z ~f. X _ NiiiiilH-r of samples % 1 Mc'ridioii circularc 347 <>1 16 Goniphon. parvul Kit) '>8 ') Navicula radiosa 2~ 4 Diatoma hiemale 258 45 19 Pinnul. vir. com 14S ">r> 5 247 43 4 >o SVM L'lua danica 148 *>6 (5 Gomphonema subclav 222 39 21 Diploneis ellipt. 140 25 7 Khopalodia gibbet 216 .'58 22 Acliiiantli. laiiccol 139 ')') $ Pinniilaria viridis '> \ 4 38 23 Epithemia turg. 1 39 '^ q Svnedra Ulna tvp 207 36 24 Coccoiii'is Placent 126 )) 10 Cvmbclla parva 200 35 25 Ceraloncis Arcus 126 >; 11 Hliopal vcutric 19(5 :54 2(5 Melos. ital. tennis . ... 123 <>>> 12 Pi n mil boreal is 195 34 27 Frustulia vulg 11(5 21 13 Tabellaria floccul 19'' 34 28 Pinnul. major 111 ''il 1 1 Hantzschia ampli 176 31 29 Tabell. fcnestr 108 1<) 1f> Diatomella Half 168 29 30 Cymb. Cistula 100 18 1 2 3 4 5 Characterising forms in 10 samples or more. Meridiem circularc 50 Diatoma hiemale 43 Synedra Ulna danica.... 41 Melosirre sp. diversse.... 37 Synedra Ulna typica .... 3(i (> I^pithoinia? sp. diverssc 7 CymbellcC sp. diverse . 8 Fragilaria? sp. diversae. 9 Ceratoneis Arcus 22 17 10 10 This table shows lhat the forms most characteristic to the Icelandic flora of fresh-water diatoms are: Meridion, Diatoma, Synedra and Melosira. Comparing the two lists it further appears, lhat the fact of a form being met with in a great number of samples not necessarily means that it is generally characterising; for inst., Navicula radiosa marked no. 2 in the first list only characterised two samples; Cymbella venlricosa, Pinnularia viridis, fiomphonema subclavalum each only one sample, while Pinnularia borealis and Hantzschia amphioxys did not characterise any. HOT SPRINGS A; "hot springs" I have only included those which on the labels have distinctly heen marked as such. I have of these 30 samples from 13 localities, viz. from S.: Grafarbakki (1 sampl.), Minni Laxa (4 sampl.), TorfastaSir (4 sampl.). S.W. : Hrossholt (1 sampl.), Reykjavik (4 sampl.). N.W.: Hrutafjordur (1 sampl.), Reykjanes (3 sampl.), Steingrims- fjordur (1 sampl.). N.: Akureyri (2 sampl.), Hrafnagil (4 sampl.), Hrisey (1 sampl.), Laugafells Laug (3 sampl.), Reykjarfjordur (1 sampl.). In these I have found the following forms: Number of hot spring's Achnanthes (17) 1 coarctata 1 2 exigua 1 3 *exilis 1 4 lanceolata .... 9 5 - fseroensis 2 6 minutissima . 3 Number of hot springs Caloneis (14) *amphisbsena . . 1 fasciata 2 *Silicula gen. . . 10 alpestris. 5 inflata. 2 Total. 20 1 Total ... 17 A ni p h o r a (8) coffaeiformis . . 1 2 *ovalis 6 3 Pediculus 3 4 protracta gall.. 2 5 veneta . 1 Ceratoneis (1) 1 Arcus 8 Total... 13 Total ... 8 Cocconeis (5) 1 flexella 2 2 Placentula. 7 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Number of hot springs Cymbella (31) aequalis 1 aspera 1 Cistula 1 cymbiform. ... 2 gracilis 2 helvetica heteropl. min. incert. navic. . *lanceolata . . . lapponica.. . . microcephala. naviculif. 3 parva 9 ventricosa . 5 Total... 33 Total... 9 Anomoeoneis (5) 1 exilis 1 2 zellensis.. 1 Cymatopleura (2) 1 Solea . 2 Denticula (3) *elegans 1 Total. 2 Total... 2 Total... 1 6* 84 ERNST 0STIU P Number of hot springs D i a t o m a (5) 1 *hiemalc 10 2 *tenue . 1 Total... 11 Din torn ell a (1) 1 Balfouriana ... 7 Total ... 7 Diploneis (8) 1 *elliptica 18 2 ovalis 1 3 oblongella 5 4 pumila . . 1 Total. . . 25 Hpithemia (11) 1 *Argus 4 2 Sorex amphic. . 1 3 *lurgida 3 4 *Zebra 15 5 longiss. ... 1 6 proboscidea 4 Total. . . 28 Eunotia :38) 1 Faba densestr. . 1 2 gracilis 1 3 impressa ang. . 2 4 lunaris 2 5 major 1 6 pedinal. minor. 1 7 polyglyphis ... 1 8 prasrupta 3 9 curta . 5 10 robusta Diad. . 1 11 Triodon. 1 Total... 19 Fragilaria (23) 1 construens .... 1 2 intermedia .... 2 3 mutabilis 1 4 intcrccdens 1 5 virescens exig. . 1 Number of hot springs F r u s 1 11 1 i a ^3) 1 rhomb, saxon.. 2 2 leptoceph. 1 3 'vulgaris 10 Total... 13 G o m p h o n e m a (23~) 1 *acuminatum . . 2 2 f. coronata 1 3 f. trigonoc. 2 4 angust. j>rod. . . 3 5 constrictum ... 1 6 gracile aurit . . 4 7 dichotom. 2 8 navicul... 1 9 parvulum 5 10 subclavatum . . 4 Total... 25 H a n t z s c h i a (5) 1 amphioxys .... 9 2 - elongata. 1 3 truncata., 1 Total ... 11 Mastogloia (3) 1 ellipt. Dans. ... 5 2 *Smithi lacust. . 1 1 2 3 Total ... 6 M e 1 o s i r a distans niv. . . . 1 ital. tenuis. ... 2 varians 4 Total. 7 Total . 6 Meridion (1) 1 circulare 12 Total... 12 Navicula (69) 1 anglica 2 2 cincta 2 3 angusta . 1 4 contenta biceps 1 Number or hot springs 5 cryptocephala . 2 (5 exilis 1 7 cusp, ambig. . . 1 8 dicephala 7 9 undulata 1 10 gracilis 1 1 1 - schizonem. 1 12 hungnr. capit. . 1 13 mutica Cohni . 3 14 nivalis 4 15 pereg. Meniscus 1 16 Puptila 3 17 pusilla 5 18 *radiosa 8 19 rhyncoceph.. . . 1 20 Rota?ana obi... 1 21 Semen 2 22 virid slesvic.. 2 Total. 51 Neidium (11) 1 at'iine amph. . . 5 2 bisulc 1 3 dubium 2 Total... 8 Nitzschia t,34) 1 amphibia 17 2 - Frauenf. . 1 3 angustata 1 4 com mut 1 5 Denticula 4 6 Frustulum .... 1 7 linearis 2 8 Nathorsti 1 9 Palea 2 10 fonticola . 1 1 1 -tenuirostris 1 12 Sigma Clausi . . 2 13 sigmoidca .... 1 14 *sinuata 4 15 *thcrmalis 3 16 minor. . 1 Total. . . 43 FRESH-WATER DIATOMS FROM ICELAND 85 Number of hot springs Fin mil aria (66) 1 *appendicul. ... 2 2 budensis 2 3 Balfouriana ... 2 4 Brandcli lin. . . 1 5 *Brebissoni .... 1 6 diminuta 1 7 *borea!is 17 8 brevicostata 1 9 brevicostata ... 3 10 diverg. ellipt. . . 1 1 1 intermedia. ... 1 12 interr. staurf: . . 5 13 lata 4 14 Legumen 1 15 longa.. . 1 16 leptosoma .... 3 17 major 4 18 mesogong 3 19 *mesolept. staurf. 5 20 angusta. 1 21 Microstauron .. 1 22 molaris 1 23 subcapit 2 24 stauropt. gen... 2 25 stauropt. interr. 26 stomatophora . 27 streptoraphe . . 28 *viridis gen. . . . 29 - commut. . 30 rupestris . Total. Number of hot springs 2 2 3 10 6 3 91 Bhoicospbenia (1 1 curvata 9 Total... 9 Rhopalodia (7) 1 *gibba 11 2 gibberula 13 3 rupestris 6 4 parallela 5 5 ventricosa .... 9 Total. . . 44 Stauroneis (4) 1 anceps 1 2 *Pboenicenteron 1 Total. 2 Number of hot springs Surirella <13) 1 ovalis minuta . 2 2 ovata . 5 Total . . 7 Synedra (17) 1 delicat. mesol. . 1 2 capitata 1 3 pulchella 1 4 rostrata 1 5 rump, fragil. . . 3 6 Ulna typica. . . 11 7 danica.. 7 Total. . . 25 Tabellaria (2) 1 fenestrata 2 2 flocculosa . 10 Total... 12 Of the forms included in above list are those found previously in hot springs in Iceland (see "La flore algologique d'eau douce de L'Islande par M. Emile Belloc. Paris 1894" p. 912) marked * (in all 23). The figures in brackets opposite the names of the genera, give the number of species and variants of the respective genus found in the material dealt with. In most of the samples from hot springs, I have found Diatoms with endochrome. ERNST 0STRUF 1 I have found the following marine forms in o of the hot springs situated in N.W. and N., near the coast. Reykjanes Hrisev Hrefnagil Steingrims- Reykjar- X.W. N. * N. fjorour fjorour Number Number Number Number Number of samples of samples of samples of samples ofsamples 1 2 Achn. brevipes ... . intermed. Amph. marina 2 1 1 1 1 4 Hiddulph aur 2 1 1 1 Gal. Liber lin 3 6 Coccon. cost. . . . 7 Scut 1 8 - staurf. . . Goscin. excent 2 1 ID Dipl. interrupts 3 11 Gramm isl 1 1? Melos. numm 1 1 Navic. bottnica 1 M Rhabd arc 1 m i n 3 1 1 Ifi Rhopal. Muse 2 1 17 Schiz. ram 2 18 Svn aff ... 2 19 Trach. asp. interm... . 1 The editors regret the presence of a few discrepancies between the list and the tables which they have not been able to remove. Possibly there may be other incorrectnesses which the author might have rectified, when going through the proof-sheets. FRESH-WATER DIATOMS FROM ICELAND 87 LITERATURE BHUN, J. Diatomees d'eau douce de Tile Jan Mayen et de la cote est du Green- land. Bih. t. K. Sv. Vet.-Ak. Handl. B. 26, Afd. Ill, No. 18. Stockholm 1901. (Br. J. M. & E. G.) CI.EVE, ASTHID. On the recent fresh-water diatoms from Lule Lappmark in Sweden. Bih. t. K. Sv. Vet.-Ak. Handl. B. 21, Afd. Ill, No. 2. Stockholm 1895. (A. Cl. Lul. Lappm.) CLEVE-EI LER, ASTHID. New contributions to the diatomaceous Flora of Finland. Ark. f. Botanik. B. 14, No. 9. Stockholm 1915. (A. Cl. Finl.) CLEVE, P. T. Farskvattens-Diatomaceer fran Gronland och Argentinska republiken. Ofvers. af Kgl. Vet.-Akad. Forh. No. 10. Stockholm 1882. (Cl. Grl. & Arg.l CLEVE, P. T. The diatoms of Finland. Act. soc. p. Flora et Fauna Fenn. VIII. No. 2. Helsingfors 1891. (Cl. Finl.) CLEVE, P. T. Synopsis of the Naviculoid Diatoms I-II. K. Sv. Vet.-Ak. Handl. B. 26, No. 2 and B. 27, No. 3 Stockholm 189495 (Cl. Syn.) CLEVK, P. T. and A. GRUNOW. Beitriige zur Kenntniss der Arktischen Diatomeen. K. Sv. Vet.-Ak. Handl. B. 17, No. 2. Stockholm 1880. (Cl. & Grun. A. D.) DE-TONI, J. B. Sylloge Bacillariearum hucusque cognitarum. Patavii. MDCCCXCI- MDCCCXCIV. (De T. Syll.) DONKIN, A. S. The natural history of the British Diatomacea?. London 187173. (Donk. Br. D.) GREGORY, W. Note of some new Species of British Fresh-water Diatoms. Quart. Journ. of Micr. Sc. London 1856. (Greg. Micr. Journ.) GRUNOW, A. Algen und Diatomeen aus dem Kaspischen Meere. Schneider, O.: Naturw. Beit. z. Remit, d. Kaukasuslander. Dresden 1878. (Grun. Rasp.) GRUNOW, A. Beise seiner Majestat Fregatte Novara um die Erde. Bot. Theil. B. 1. Algen. Wien 1867. (Grun. Nov.) GRUNOW, A. Beitrage zur Kenntniss der fossilen Diatomeen Osterreich-Ungarns. Beitr. z. Pala?ont. Oest.-Ung. u. des Orients. B. II. Wien 1882. GRUNOW, A. Die Diatomeen von Franz-Josefs Land. Denk. Akad. Wiss. Wien. B. XLVIII. Wien 1884. (Gr. Fz.J.) HEIBERO, P. A. C. Conspectus criticus Diatomacearum Danicarum. Rjohenhavn 1863. (Heib. Consp.) HKHIRAUD, J. Les Diatomees d'Auvergne. Paris 1893. (Her. Auv.) HERIHAIO, J. Les Diatomees fossilcs d'Auvergne. Paris 1902. 1903, 1908. (Her. foss. Auv.) HUSTEDT, FRIEDERICH. Bacillariales aus den Sudeten und einigen benachbarten Gebieten des Odertales. Arch. f. Hydrobiol. u. Planktonk. B. X, 1914. Stuttgart 1914. (Hust. Sud.) JUHLIN-DANNFELT. On the Diatoms of the Baltic Sea. Bih. t. K. Sv. Vet.-Ak. Handl. B. 6, No. 21. Stockholm 1882. (Danf. Bait.) 88 ERNST 0STRI 1': FRESH-WATER DIATOMS FROM K.KI.AND LAGERSTEDT. N. (i. W. Sotvattens-Diatomaceer fran Spetsbergen ocli Beeren-Eiland. Hih. t. K. Sv. Vet.-Ak. U.I. No. 11. Stockholm 187.1 (Lgst. Spl. MEISTER. FH. Die Kieselalgen dcr Schweiz. Bern 1912. (Meist. Sehw. Mfi.i.Eit, OTTO. Bacillarien aus dem N'yassalande und einigen benachbarten Ge- l)ietcn. Hedwigia XXXIV- & XXXVI. 1895 and 1897. (O. M. Nyas. MOi.i.KR, OTTO. Rhopalodia. Kin neues Genus der Bacillarien. Hot. .Jalirb. XXII. 1899. i(). M. Hhop.; MTLLEK, OTTO. Sprunjjweise Mutation bei Melosirecn. Ber. d. Deut. Bot. Gesellsch. 190:J. B. XXI. II. (i. Berlin 1903. (O. M. Mut.j Mf LLEH, OTTO. Pleomorphismus, Auxosporen und Duucrsporen bei Melosira-Arten. Jalirb. f. wiss. Bot. B. XLIII, H.I. Leip/itf 1906. (O. M. PI.) MI'LLKH. OTTO. Bacillariacecn aus Sud-Patagonien. Kngl. Bot. Jahrb. B. XLIII. H. 4. Beibl. 100. Leipz. 1909. ^O. M. Pat. OSTEXKKI.D. G. H. and C. WESENBERG-LuND. A regular Fortnightly Exploration of the Plankton of the two Icelandic Lakes. Thingvallavatn and Myvatn. Proc. of the Roy. Soc. ofKdinb. Vol. XXV. Part XII. Kdinburg 1906. (Ost. Thing\ . PANTOCSEK, .1. Die Bacillarien des Balatonsees. Result, d. \\issensch. Erforsch. d. Bal.-sees. B. II. Teil II. Section I, Anhang. Wien 1902. Pant. Bal.) PAXTOCSEK, .1. Bacillarirc Lacus Peisonis. Pozson\ r 1912. Pant. Peis.) PANTOCSEK, .1. Beitn'ige /.ur Kenntniss der fossilen Bacillarien Ungarns I-III. Na^y- Tapolcsany 1886 and 1889. Pozsony 1905. (Pant. toss. L'ng.) SCHMIDT, ADOLF. Atlas der Diatomaceenkunde. Aschersleben 1874. not yet com- pleted. (A. S. Atl.) SMITH. \\ . Synopsis of the British Diatomaceae I-II. London 1853 and 1856. i^W. Sm. Syn.) STHOSK. K. Das Bacillarienlager bei KlicUen in Anhalt. Fcstsch. d. XXXVII Versaml. deut. Philol. und Scjiulm. zu Dessau. Dessau 1884. (Str. Klik.) VAN HEURCK. H. Synopsis des Diatomees de Bclgique I-I\'. Anvers 1880 85. (V. H. Syn. VAN HKUHCK. II. Traite des Diatomees. Anvers 1899. V V. H. Trt.) OsTiu'i'. ERNST. Ferskvands Diatomeer fVa Ostgronland. Medd. om Gronl. XVIII. Kjobenhavn 1897. (Ost. Ostg. F.) 0STIUP, ERXST. Fresh-water Diatoms of the F;iToes. Bot. of the F;vr. I. Copen- hagen and London 1901. ^Ost. Fser.) OSTIU r. EKNST. Beitriige zur Kenntniss der Diatomeenflora des Kossogolbeckcns, Hedwigia. B. XLVII1. (Ost. Koss.) OSTHUP. ERNST. Danske Diatomeer. Kjobenhavn 1910. (Ost. I). D.) EXPLANATION OF PLATES All the figures were drawn with a magnification of 100 diameters and reduced in reproduction to 670 diameters 90 PLATE I. Fig. 1. Caloneis Fedderseni sp. nov. 2. Caloneis islandica sp. nov. 3. Caloneis Jonssoni sp. nov. 4. Caloneis procera sp. nov. 5. Neidium incurvum (Greg.) 0st. 6. Neidium islandicum sp. nov. 7. Neidium lineare sp. nov. 8. Neidium panduriforme sp. nov. 9. Diploneis ovalis (Hilsej Cl. f. subinflata. 10. Diploneis subovalis Cl. 11 Frustulia islandica sp. nov. 12. Navicula Bacillum Ehr. var. densestriata var. nov. 13. Stauroneis anceps Ehr. var. elliptica var. nov. 14. Stauroneis bifissa sp. nov. 15. Stauroneis elegantula sp. nov. 16. Stauroneis parvula Grun. var. capitata var. nov. 17. Stauroneis perexilis sp. nov. Kiitnny nl h-chind Vol. II. (Oslriij) . PLATE 1. 6 . to 12 E. Ostrup del. 16 92 PLATE II. Fig. 18. Stauroneis Stefanssoni sp. nov. - 19. Cymbella Cistula Hempr. var. Caldogastensis Prud. - 20. Cymbella dubia sp. nov. - 21. Cymbella islandica sp. nov. - 22. Cymbella Jonssoni sp nov. - 23. Cymbella linearis sp. nov. - 24. Cymbella marginata sp. nov. - 25. Cymbella recta sp. nov. - 26. Cymbella subconstrieta sp. nov. - 27. Gompbonema irregulare sp. nov. - 28. Gomphonema islandicum sp. nov. - 29. Gompbonema medio-constrictum sp. nov. of Iceland. Vol. II. I'Ostnip.. . II. 21 26 ' 23 K. Ostrup del. 29 27 94 PLATE III. Fig. 30. Navicula anguste-t'asciata sp. nov. - 31. Navicula Boyei sp. nov. - 32. Navicula curte-striata sp. nov. - 33 Navicula dicephala (Ehr.) W. Sm. var. undulata var. nov. 34. Navicula exilior sp. nov. - 35. Navicula Fustis sp. nov. - 36. Navicula islandica sp. nov. - 37. Navicula Jonssoni sp. nov. - 38. Navicula lyrigera sp. nov. - 39. Navicula Ostenfeldi sp. nov. - 40. Navicula pinnularioides sp. nov. - 41. Navicula semiiasciata sp. nov. - 42. Navicula spatiata sp. nov. 43. Navicula Thingvalhu sp. nov. - 44. Pinnularia leptosoma Grim. var. undulata var. nov. - 45. Pinnularia perexilis sp. nov. 46. Pinnularia hryophila sp. nov. 47. Pinnularia islandica sp. nov. 48. Pinnularia karelica Cl. var. rostrata var. nov. - 49. Pinnularia alpina W. Sm. var. linearis var. nov. - 50. Pinnularia borealis Ehr. var. brevicostata Must. 51 Pinnularia lata Breb.) Cl. forma minima. 52. Pinnularia Brandeli Cl. 53. Pinnularia densestriata sp. nov. 54. Pinnularia brevicostata Cl. var. islandica var. nov. Botany of Iceland. Vol. II. I'Ostrup . PLATE III. 30 32 37 33 38 47 'JO K. Ostrup del. 52 53 96 PLATE IV. Fig. 55. Pinnularia parva (Greg.) Cl. var. minuta var. nov. - 56. Pinnularia subundulata sp. nov. .")7. Pinnularia Thoroddseni sp. nov. .">8. Pinnularia gigantea sp. nov. - 59. Amphora dubiosa sp. nov. - 60. Achnanthes Boyei sp. nov. 61. Achnanthes coarctata Bres.^ Cl. forma. - 62. Achnanthes lanceolata (Bres.) var. subinflata var. nov. - 63. Surirclla asymmetrica sp. nov. 64. Surirella granulata Ost. var. elliptica var. nov. - 65. Surirella islandica sp. nov. - 66. Surirella Jonssoni sp. nov. - 67. Campylodiscus sp. BoLniy i)l Iceland Vol. II. (Ostrup). 1'LVI'K I \' 59 6! 60 i. 62 63 6* 65 67 66 E. 0strup del. Botany of Iceland. Vol. II. 98 PLATE V. Fig. US. Hant/sdiia dubravicensis Grim. - 09. Hant/scliia trimcata sp. nov. 70. Hant/scliia forma abnormis. 71. Nit/.schia angustata \V. Sin.) (irun. forma. 7'J. Nit/.schia Jonssoni sp. nov. 7.'5. Nit/schia glaberrima sp. nov. 74. Nitzscbia mucronata sp. nov. 7."). Kunotia islandica sp. nov. 76. SyiR'dra rumpens Ktz. var. islandica var. nov. 77. Syncdra I'lua (Nitzsch) Ehr. f. arcuata. 7.S. Fragilaria Bacillus sp. nov. 7i). Fragilaria mutabilis W. Sm.) Grun. var. inflata var. nov - 80. Fragilaria rbombica sp. nov. ( S1. Fragilaria triuudulata sp. nov. - 82. Fragilaria undata YV. Sm. forma. - 83. Denticula islandica sp. nov. 84. Melosira Stcfanssoni sp. nov. Botany of Iceland. Vol. II. (Ostrup). PLATK V. 68 . 73 69 ' 70 76 78 82 E. Ostrup del. 83 (1 THE LICHEN FLORA AND LICHEN VEGETATION OF ICELAND BY OLAF GALL0E PH. D. 19191920. INTRODUCTION. IN 1913, after deliberation with Professor E. Warming, I made a journey to Iceland to investigate the island lichenologically, as far as this could he done during the course of one summer. I had visited the island once before, (1906) and had become interested in its lichen-vegetation, which impressed me as presenting many features of great interest. At that time I had, however, very little opportunity of making investigations, therefore I eagerly seized the opportunity of investigating the lichens, which offered itself in 1913. Already, before this last journey, I had studied the lichen-vegetation more thoroughly in the different plant-associations of Denmark, and had published my investigations on this subject in 1908; afterwards (in the early summer of 1913) I published my "Forberedende Under- sogelser til en almindelig Likenokologi" ("Introductory Investigations concerning a general Lichen-Ecology"), and was therefore now highly interested in extending my investigations to a country, which was not situated in the same climatic zone as Denmark, because I might expect to find there essentially different vegetational and floral con- ditions; and I was not disappointed with regard to this point. I made collections and notes as assiduously as the somewhat dif- ficult conditions of travelling permitted, but I am sorry to say that I must admit, in my own case and probably in that of others also, that Iceland is too large to survey fully during one summer's travel. However, I hope, and also believe, that the descriptions I have been able to give below, will not be altered essentially by investiga- tions, which may possibly be made by future travellers. The districts which I investigated most thoroughly were those 104 OLAF GALL0E around Rey5arfjor<5ur and Sey5isfj6r5ur on the cast coast, the country around Husavik and EyjafjorQur on the north coast, Isafjorftur on the north-western peninsula, Reykjavik and HafnarfjorfHir in South-west Iceland, the districts around Mvvatn, Jokulsa and Laxa in the in- terior of North Iceland proper, and the districts about Thingvellir and Geysir. In addition, I paid a flying visit to the islands of Vest- ma nnaey jar. I had a fairly good opportunity of investigating these districts somewhat thoroughly. But unfortunately, on the other hand, I had no chance of seeing anything worth mentioning of the desert-interior of Iceland. Among other specially interesting localities were the numerous sea-fowl cliffs along the coasts: no doubt these would prove remarkable in many ways, but I had no opportunity of making independent observations in such spots. The results of these investigations I have embodied in the fol- lowing Lichen Flora (which, by my work, contains a fairly con- siderable number of species not found previously,) and Lichen Ve- getation of Iceland; this latter subject has been studied only par- tially and not at all exhaustively by others (Gronlund and Helgi .1 o us son). As regards the literature on the subject, reference should be made to Dei chman n Branth's "Liehenes Islandia 1 " (Botanisk Tids- skrift, vol. 2.'), l<)0,'i) in which all lichenological literature pertaining to Iceland has been enumerated, and a full record of collectors and collections from Iceland has been given. It is the newest and most exhaustive list of species, but now to it must be added those species which have subsequently been found by me. I have been obliged to make a few minor alterations in Branth's list, as the genus Kndococcus can scarcely be maintained any longer as a lichen-genus, and is therefore omitted from the following list. A full description of the conditions pertaining to vegetation in Iceland, and the references to literature will be found in the part of the present work (vol. I) written by Professor Thoroddsen. These two aids to the study of the literature are very exhaustive. As regards the ecological and other biological conditions, I must refer the reader to my two papers mentioned above, "Danske Li- keners 0kologi" (Bot. Tidsskrift, vol. 28, 1 ( .)()8) and "Forberedende Unders0gelser til en almindelig Likenokologi," (Dansk botanisk Ar- kiv, vol. I, no. 3, 1913). In these papers full references will be LICHENOLOGY OF ICELAND 105 found to all the literature of the biology of Lichens, so that it is unnecessary to cite it more particularly here. The Directors of the Carlsberg Fund have, with their usual generosity, supplied the funds for the investigations and for the journey to Iceland ; for which I tender my best thanks to the said Directors. I. THE LICHEN FLORA OF ICELAND. THERE is hardly any other group of plants in which the boundary line between the species is so indefinite as it is in the Lichens. Several types are easy to describe, and readily recognizable after description, but between such readily recognizable types there fre- quently occur so many intermediate forms, that we are quite per- plexed in deciding to which type or species - - or whatever we now choose to call it the plant in question should be referred, when it is to be included in a list of species. No doubt the majority of botanists have occasionally tried to determine, for instance, some or other Cladonia-species and have thereby experienced for them- selves the difficulties which thus arise. But as with Cladonid, so is it with the majority of the genera, only, in many cases, the dif- ficulties are even more considerable. To the less skilful investiga- tors any sure determination is usually impossible, but even for the best-trained lichenologist, it is often extremely difficult to identify a species which he has before him, with one already known and described by others, a circumstance which has caused much contro- versy, to a great extent unnecessary, between the "patres" of lichen- systematology. The reason of this richness of forms, this abundance of forms intermediate between the most easily distinguishable types, is not known. We may naturally form our surmises on the subject. It may be assumed that the lichen-group, taken as a whole, is a group in process of rapid development, that is to say, in the act of forming numerous new species which, in the course of lime, will separate themselves into a smaller number of easily distinguishable species, through many of the intermediate forms dying out. Or we may suppose that the types in themselves are few, but possess a wide, LICHENOLOGY OF ICELAND 107 individual range of variations, which is the reason that the boundary line between the species, is difficult to distinguish. But this is, at present, mere assumption, and as such will not be discussed here more fully. I shall only remark, that any certain decision on the matter can only result from making experimental cultures with the types along the lines, on which researches on heredity are now carried out. But unfortunately we have far to go before we reach this stage, for lichens are generally very difficult to cultivate and, in addition, grow very slowly, so that they would not give quick results. This best mode of separating the species the experimental mode will perhaps never be followed by any one. The next- best method which, indeed, must form the introduction to the experimental method has not been adopted to any extent by lichenologists. I shall now brielly explain what I mean. In order to be able to decide how many types (species) there exist, it is absolutely necessary to follow quite another method than that hitherto followed by lichenologists. From the infancy of lichen- ology up to the present time, the systematists, dazzled by Linne's short, emphatic diagnosis of higher plants, have endeavoured to create a similar diagnosis for the lichen-species. Anything like this is however impossible, and has caused the greater part of the systematic chaos in which we now find ourselves. If we bear in mind what I wrote above on the abundance of the intermediate forms, and the absence of corresponding boundary lines, it is self- evident that each single type must be described and figured as exhaustively as possible, in order to be recognized by other workers. The only sure means of making a type recognizable for others is to examine, figure and describe one single individual of the type, making sure that we do not unintentionally confuse two nearly allied types together in one mixed description, as for instance might happen through investigating the thallus of one specimen and the apothecium of another. This method, which has as yet never been practised in works on lichen-systematology, (I myself have, however, material in hand, not published, for some type-descriptions of such a kind), will be the only means of distinguishing the types from each other, and of eventually forming an introduction to culture-experiments, (which as already mentioned must begin with well-defined types), so that 108 OLAF GALI.oi-. we may finally emerge from the systematic and synonym-chaos in which \ve now find ourselves. The method in question involves however a certain danger, as it might end in our establishing almost every individual in the O C7 . world as a distinct type. And a danger just like this can only be avoided by proving once for all, at some future time, by culture- experiments, how many of the types established by thorough ob- servations and descriptions, are so nearly related to each other, that they must be referred to the same species. It is clear that this "method of individuals," as I will call it, will be able to revolutionize our apprehension of species, and is for the time being the only way out of the difficulty. But it is equally clear that such a method is not a brief a flair, which the individual investigator can accomplish with regard to more than a very restricted number of types. Lists of species and local floras - and also the present one - must consequently still be worked out according to the prevalent, old-fashioned principles, although, as I have been working with them, I have gradually become convinced of their drawbacks, and of how obsolete and defective they are. Let us therefore briefly regard these defects and the lichen- synonymy, in order better to understand their nature. The greatest defects of the lichen-systematology lie in the fact, thai the one group of investigators are greatly inclined to include as many forms as possible in one large comprehensive species, while others (and these the majority) are inclined to separate the species into many smaller species, each with its o\vn name. In the former group may be reckoned for instance Dei chin aim Bra nth in Den- mark. This tendency of his to restrict the number of the species, runs as a leading thread through his works on the lichens of Ice- land, Greenland and Denmark, and what I cite from his works in my following list will prove this in several instances. I must, how- ever, acknowledge that his observations on species, and his critical remarks on the "species" of other investigators, have several times struck me on account of their original and clear-sighted view of the relationship and genealogical affinity of the species. I am not to be understood to concede that this investigator can prove, for instance, that Cladonia uncialis and C. ainanrocroea (just to give one single example) are really genealogically allied, whilst others classify them as two distinct species; but Deichmann Branth's sug- gestions regarding this point, and his many other critical remarks LICHENOLOGY OF ICELAND 109 on the unity where others see diversity of species, show a com- prehension of the relationship of the lichens which, I believe, will prove to contain many truths when once, at some future time, we succeed, by experiments, in clearing up the limitation of the species. But it should be borne in mind that, for the time being, his systematic considerations (which are excellent according to my opinion) are theories, pure and simple, which experiment alone can set upon a firm foundation, and Deichmann Bra nth him- self must have had a clear understanding of this. It is only to be hoped that, one day, the necessary culture-experiments will be made, which will eventually do that justice to his considerations, which up to the present, has been too scanty. To the other group of investigators belong virtually all the lichenologists of the present day - all those who so often establish species upon quite slight peculiarities of structure in the individuals considered. The inconveniences this causes with regard to the synonymy of the lichens, is evident. The same name is sometimes used in a limited and sometimes in a very wide sense. The same species is sometimes referred to one, and sometimes to another genus. This creates a confusion, which in several cases, is simply impossible to reduce to order. In order to clear away the difficulties with regard to synonyms, it has been the custom from the earliest times, to preserve in mu- seums "original specimens," i. e. the specimens on which the author has founded his species. This custom is very commendable, but by no means so satisfactory, as we are frequently inclined to be- lieve; the fact being that lichens alter rather essentially in the course of time, frequently change colour, and alter their chemical reactions, etc., to say nothing of the fact that the specimen may not be cut up to ascertain the anatomical resemblance between it and other specimens, the identity of which is wished to be ascertained; and without such anatomical investigation, comparison is simply worth- less in all difficult cases. This fact should be emphasized in order to remove, once for all, the entire foundation built up under the persistent worship of "original specimens." We must demand that the author of the species should describe his species well, and not only leave some gnawed or doubtful original specimen, which is respected so highly that no one dares to dissect it, and thereby deprive it of its importance, while often the very specimen proves, 110 OLAF GALL0E on closer investigation, to he an intermixture of individuals of fairly different species, and \ve are unable to decide, with any certainty, the individual for the sake of which the author has left it in trust for after times! Else we must yield to the inevitable, viz., that lichen determinations become rather uncertain, as they also prove to be in many cases, or that later lichenologists shall simply disregard the oldest author's right of priority, and re-establish the species with better definition. It is absolutely necessary to get away from the exaggerated belief in the principle of "original specimens." The following list of the lichens of Iceland, as indicated above, is not based on my own studies of the species, according to the "method of individuals" mentioned above, that would be an almost impossible work for one man, but is arranged in com- pliance with the frequently -employed limitation of species, as they are presented to us in the commonly known lichenological works of Th. Fries, Crombie, Koerber, Ny lander and others; the list, consequently, has the synonymic and systematic weaknesses belonging to the works in question, but also has their strong point, viz., it can safely and easily be compared with other lists worked out on the same principles, a thing rather necessary for lichen- ological reasons. In the list given I have drawn special attention to the species which were found by myself as "new to Iceland," and which are not found in Deichmann Bra nib's list of 190,'i The reason why these species have been specially mentioned is simply that I am myself responsible for their correct identification, and not that special attention might be drawn to these new finds, and this so much the less, as I cannot see anything specially meritorious in finding new species; every well-trained collector can do so much. The following list by no means renders Deichmann Branth s excellent work superfluous. In his work we find geographical sta- tions for all the species, and my own list merely supplements his by describing more fully the species new to Iceland, and by 1110- derni/ing his limitation of species, making it more in agreement with the demands of the time, without necessarily constituting a real improvement in the apprehension of the species, which, as already mentioned, will not be attained except by detailed investiga- tions in the future, according to my "method of individuals." The following species have been found: LICHENOLOGY OF ICELAND 111 I. PYRENOCARPEjE. VERRUCARIACE.E. (Microglaena, Polyblastia, Staurothele, Verrucaria.) Microglaena. M. sphinctrinoides Nyl. (D. B., p. 220, under Pyrenula) 1 . This species is wanting in Greenland. Polyblastia. P. hyperborea Th. Fi. On Basalt, Seydisfjord, O. Galloe, 1913. New to Iceland. P. Henscheliana Koerb. (D. B., p. 220, Pyrenula). Absent from Greenland. Great Britain (Crombie) 2 . Staurothele. S. clopima Wnbg. (D. B., p. 220, Pyrenula). G. Brit. Verrucaria. V. margacea Wnbg. (D. B., p. 219, with var. aethiobola Wnbg.). Absent from Greenland. G. Brit. V. maura Wnbg. (D. B., p. 219). Greenland. G. Brit. V. mucosa Wnbg. (D. B., p. 219). Greenland. G. Brit. V. nigrescens Pers. (D. B., p. 219). Absent from Greenland. G. Brit. V. rupestris Schrad. (D. B., p. 219). Greenland. G. Brit. DERMATOCARPACE-E. (Dermatocarpon.) Dermatocarpon. D. cinereum Pers. (D. B., p. 219, Verrucaria). Not found in Greenland. G. Brit. D. hepaticum Ach. (D. B., p. 219). Greenland. G. Brit. D. miniatum L. />'. complicatum Sw. (D. B., p. 219). Greenland. G. Brit. 1 Deichmann Branth : Lichenes Islandise, Botanisk Tidsskrift. 1903, vol. 25. 2 Crombie: British Lichens, 18941911. 1 1 2 OLAF GALL0E PYRENULACE.E. Arlhopyrenia, Microthdia.) Arthopyrenia. A. analepta Adi. (D. B., p. 220, Sagedia, with f. punctiformis Adi.). Greenland. G. Brit. A. grisea Sdilddi. (D. B., p. 220, Sagedia). (ircenland. Not found in G. Brit. Microthelia. M. micula Plot. (D. B., p. 220). Not found in Greenland. G. Brit. II. CONIOGARPINE^E. CALICIACE.E. (Coniocybe). Coniocybe. C. furfuracea L. (D. B., p. 220). Greenland. G. Brit. (Sphaerophorus). Sphaerophorus. S. coralloides Pers. (D. B., p. 220, Sphaerophoron). Greenland. G. Brit. S. fragilis L. (D. B., p. 220, Sphaerophoron). Greenland. G. Brit. III. GRAPHIDINE^E. ARTHONIACE^:. (Arthonia.) Arthonia. A. proximella Xyl. (D. B., p. 219). Greenland, G. Brit. A. punctiformis Adi. (D. B., p. 219). Not found in Greenland. G. Brit. A. ruderalis Nyl. On tuff, Reydarfjord, O. Galloe, 1913. NY NY to Iceland. G. Brit. LICHENOLOGY OF ICELAND 113 IV. CYCLOCARPINEjE. DIPLOSCHISTACE^:. (Diploschistes). Diploschistes. D. scruposus L. (D. B., p. 212, Urceolaria). Greenland. G. Brit. GYALECTACE.E. (Gyalecta.) Gyalecta. G. cupularis Ehrh. (D. B., p. 217). Not found in Greenland. G. Brit. G. geoica Ach. Upon moss on blocks of basalt, Seydisfjord, O. Galloe, 1913. New to Iceland. G. Brit. G. foveolaris Ach. (D. B., p. 217). Not found in Greenland. G. Brit. / COENOGONIAGE^E. (Coenogonium, Racodium). Coenogonium. C. ebeneum Dillw. (D. B., p. 202, Cystocoleus). Not found in Greenland. G. Brit. Racodium. R. rupestre Pers. On basalt, Seydisfjord, O. Gall0e, 1913. New to Iceland. G. Brit. LECIDEACE.E. (Bacidia, Lecidea, Rhizocarpon, Catillaria, Lopadium, Toninia). Bacidia. B. abbrevians Nyl. (D. B., p. 217, Gyalecta). Not found in Greenland and in G. Brit. B. atrosanguinea Schaer. (D. B., p. 216, Gyalecta). Not found in Greenland. G. Brit. B. arceutina Ach. (D. B., p. 217, Gyalecta, with var. egenula Nyl. and var. albescens). Not found in Greenland. G. Brit. The Botany of Iceland. Vol. II. o 1 14 01. Al GALL0E B. Beckhausii Koerh. (D. B., p. 217, Gyalecta). Not found in Greenland. G. Brit. B. caudata Nyl. (D. B., p. 21(5, (iyalecta). Not found in Greenland, (i. Brit. B. (Bllimbia) coprodes Koerh. On pebbles. Husavik N. Iceland , O. Gallee. New to Iceland. B. (Arthrorhaphis) flavo-virescens Dicks. D. B., p. 21 7, Mycobacidia). Greenland. G. Brit. B. herbarum Hepp. (I). B., p. 217, Gyalecta). Not found in Greenland. G. Brit. B. milliaria Fr. (I). B., p. 21(5, (iyalecta). Not found in Greenland. G. Brit. B. obscurata SommeiT. (D. B , p. 21(5, Gyalecta). Greenland. G. Brit. Var. microcarpa Th. Fr. was also found. B. rubella Khrh. (I). B., p. 210, Gyalecta). Not found in Greenland. G. Brit. B. sphaeroides Sommerf. (D. B., p. 216, (iyalecta). Greenland. G. Brit. B. squalescens Nyl. (D. B., p. 215, Gyalecla). Not found in Greenland. G. Brit. B. subfuscula Nyl. (D. B., p. 210, Gyalecta). Greenland. B. umbrina (Ach.) Br. & Roslr. (D. B., p. 217, Gyalecta). Greenland. G. Brit. Lecidea. L. aglaea Sommerf. (D. B., p. 214). Greenland. L. alpestris Sommerf. (D. B., p. 215). Greenland. G. Brit. L. arctica Sommerf. (D. B., p. 215). Greenland. G. Brit. L. arctogena Th. Fr. On palagonite-mountains south of Husavik, N. Iceland, O. Galloe, 1913. New to Iceland. L. assimilata Nyl. \\\(h v. infuscala (I). B., p. 215). Greenland. L. atrobrunnea Ham. \D. B., p. 215). Greenland. L. atrorufa Dicks. (D. B., p. 212, Psora). Greenland. G. Brit. L. auriculata Th. Fr. (D. B., p. 214). Greenland. G. Brit. L. Berengeriana Mass. (D. B., p. 21.'}). Greenland. G. Brit. LICHENOLOGY OF ICELAND 115 L. cinereoatra Ach. Pebbles on mountain south of Husavik, N. Iceland, O. Gall0e. 1913. On lava near Havnefjord, SW. Iceland, O. Galloe, 1913. New to Iceland. L. confluens Fr. (D. B., p. 214). Greenland. G. Brit. L. contigua Hoil'm. with var. flavicunda Ach., macrocarpa D. C. and platycarpa Ach. (D. B., p. 214). Greenland. G. Brit. L. convexa (Fr.) Th. Fr. On lava near Havnefjord, SW. Iceland, O. Gall0e, 1913. On the moun- tain south of Husavik, N. Iceland, O. G., 1913. New to Iceland. L. crassipes Th. Fr. (D. B., p. 215). Not found in Greenland. L. crustulata (Ach.) Koerb. On pebbles, mountain south of Husavik in N. Iceland, O. Gall0e, 1913; on stones, high on the mountains, Ofjord, in N. Iceland, O. G., 1913. New to Iceland. L. cuprea Sommerf. (D. B., p. 213). Greenland. G. Brit. L. cyanea (Ach.) Th. Fr. (D. B., p. 214, L. tesellata). Greenland. L. decipiens Ehrh. (D. B., p. 212, Psora). Greenland. G. Brit. L. decolorans Hoffm. (D. B., p. 213). Greenland. G. Brit. L. Diapensiaa Th. Fr. (D. B., p. 213). Not found in Greenland. L. Dicksonii Ach. (D. B., p. 215, L. atroferrata v. Dicksonii). Greenland. G. Brit. L. elaeochroma Ach. (D. B., p. 213, L. enteroleuca with var. mus- corum Wulf., achrista Sommerf., Laureri Hepp., latypea Ach., pilularis Dav., dolosa Ach.). Greenland. G. Brit. L. elata Sch^r. (D. B., p. 214). Greenland. L. erratica Koerb. Vertical face of basalt, Seydisfjord, 0. Gall0e, 1913. New to Iceland. L. erythrophaea Flk. (D. B., p. 213). Greenland. L. furvella Nyl. Lava near Reykjavik, O. Galloe, 1913. New to Iceland. L. fusca Schaer. (D. B., p. 212). Greenland. 8* 1 1() OLA1 (i.M.I.DI L. fuscescens So mm erf. (D. B., p. 212). Greenland. G. Brit. L. fuscoatra Ach. I). H., p. 215). Greenland. L. granulosa (Khrh.) Schirr. On birch, Reykjavik in N 7 . Iceland, (). Galloe, 1913. New to Iceland. L. helvola (Koerb.) Th. Fr. (D. B., p. 213, L. vernalis f. helvola). L. lapicida (Ach.) Fr. (D. B., p. 214). Greenland. G. Brit. L. limosa Ach. (D. B., p. 215). Greenland. G. Brit. L. lithophila Ach. (D. B., p. 214). Greenland. G. Brit. L. lugubris Sommeii. (D. B., p. 212, Psora). Greenland. G. Brit. L. lurida Sw. (I). B., p. 212, Psora). Greenland. G. Brit. L. neglecta Xyl. (I). B., p. 215). Not found in Greenland. G. Brit. L. Nylanderi An/i (D. B., p. 213). Not found in Greenland. L. panaeola Ach. (D. B., p. 214). Greenland. G. Brit. L. pantherina (Ach.) Th. Fr. (D. B., p. 214; L. polycarpa). Greenland. L. paupercula Th. Fr. Lava near Reykjahlid near Myvatn, O. Gall0e, 1913; stones, high on the mountains, near fjord, O. G., 1913. New to Iceland. L. ramulosa Th. Fr. On earth near Hals parsonage, N. Iceland. O. Galloc, 1913. New to Iceland. L. rubiformis Wahlcnhg. (I). B., p. 212, Psora). Greenland. G. Brit. L. Siebenhaariana Koerb. Uppermost bare summit of the mountain of "Sulur" near O fjord, O. Galloe, 1913. New to Iceland. L. speirea Ach. (D. B., p. 214). Not found in Greenland. G. Brit. L. subconfluens Th. Fr. Gravelly soil on the mountain of "Sulur" near Ofjord, O. (ialloe. 1913. New' to Iceland. L. tenebrosa Flol. (D. 15., p. 215). Greenland. G. Brit. L. Tornoensis Nyl. (I). B., p. 213). Greenland. LICIIKXOLOGY OF ICELAND 117 L. uliginosa Schrad. (I). B., p. 213). Greenland. G. Brit. L. vernalis (L.) Ach. (D. B., p. 213). Greenland. G. Brit. Rhizocarpon. R. alboatrum Th. Fr. v. epipolia Ach. (D. B., p. 218, Buellia). Not found in Greenland. G. Brit. R. calcareum Weis. (I). B., p. 218, Buellia). Greenland. G. Brit. R. geminatum (Fw.) Th. Fr. (D. 13., p. 218, Buellia). Greenland. G. Brit. R. geographicum (L.) B.C. (D. B., p. 218, Buellia). Greenland. G. Brit. R. petraeum Wulfen. (D. B., p. 218, Buellia, including the species R. grande Arn., distinctum Th. Fr., obscuratum Th. Fr.). R. viridiatrum Flk. (D. B., p. 218, Buellia). Not found in Greenland. G. Brit. Catillaria. C. athallina (Hepp.) Hellh. On earth near Einarstadir parsonage, N. Iceland, O. Galloe, 1913. New to Iceland. C. cumulata Sommerf. (D. B., p. 216, Gyalecta). Greenland. G. Brit. C. Jemtlandica Th. Fr. (D. B., p. 216, Gyalecta). C. tenticularis Ach. (D. B., p. 216, Gyalecta). Not found in Greenland. G. Brit. Lopadium. L. fuscoluteum Dicks. (D. B., p. 218, Buellia). Greenland. G. Brit. L. pezizoideum (Ach.) Koerb. (D. B., p. 218, Buellia). Greenland. G. Brit. Toninia. T. squalida (Ach.) Nyl. (D. B., p. 216, Gyalecta squarrosa). Greenland. G. Brit. T. syncomista (Flk.) Th. Fr. (D. B., Gyalecta). Greenland. G. Brit. T. vesicularis HofTm. (D. B., p. 215, Gyalecta). G. Brit. 118 OLAF GALL0E CLADONIACE/E. (Baeoniyrrs, Claclonia, Stereocaulon). Baeomyces. B. byssoides (L.) Th. Fr. (I). B., p. 212, Sphyridium). Not found in Greenland. G. Brit. B. placophyllum Wahlenbg. (I), B., p. 212, Sphyridium). Not found- in Greenland. G. Brit. Cladonia. C. amaurocraea (Flk.) Schaer. (D. B., p. 202, under C. uncialis). Greenland. G. Brit. C. bellidiflora (Ach.) Schaer. (D. B., p. 202). Greenland. G. Brit C. cariosa (Ach.) Spreng. (D. B., p. 201). G. Brit. Not found in Greenland. C. coccifera (L.) Willd. (D. B., p. 201, C. cornucopioides). Greenland. G. Brit. C. decorticata (Floerke) Spreng. (D. B., p. 201). Greenland. C. fimbriata (L.) Fr. (D. B., p. 201). Greenland. G. Brit. C. Floerkeana (Fr.) Sommerf. (D. B., p. 201). Greenland. G. Brit. C. foliacea (Hudg.) Schaer. (D. B., p. 201, C. alcicornis). Greenland. G. Brit. C. furcata (Huds.) Schrad. (I). B., p. 201, with var. subulata Flk., racemosa Hoffm. and pungens Ach.). Greenland. G. Brit. C. gracilis (L.) Willd. (D. B., p. 201, with var. chordalis Flk., cervi- cornis Ach. and firma Nyl.). Greenland. G. Brit. C. pityrea (Floerke) Fr. (D. B., p. 201, under C. pyxidata). G. Brit. C. pyxidata (L.) Fr. (D. B., p. 201, with var. pityrea Flk.). C. rangiferina L. (D. B., p. 201, with var. silvatica Hofl'm.). Greenland. G. Brit. C. rangiformis HolTm. On earth among Empetrum, Sey&isfjord, (). Galloe, 1913. New to Iceland. C. uncialis (L.) Web. (D. B., p. 202, with var. adunca Wahlenbg. and amaurocraea Flk.). Greenland. G. Brit. LICHENOLOGY OF ICELAND 119 C. turgida (Ehrh.) Hoffm. On earth, the mountain of "Snlur" near (") fjord, N. Iceland, O. Gall0e, 1913. New to Iceland. Stereocaulon. S. condensatum Hoffm. (D. B., p. 201). Not found in Greenland. G. Brit. S. coralloides Fr. Empetrumheath, SeyiMsfjord, O. Galloe, 1913. New to Iceland. S. denudatum Flk. (D. B., p. 201, especially v. pulvinatum Schaer.) Greenland. G. Brit. S. evolutum Graewe (D. B., p. 201). Greenland. G. Brit. S. incrustatum Flk. On earth, Reydarfjord, East Greenland, O. Galloc, 1913. New to Iceland. S. paschale (L.) Fr. (D. B., p. 201). Greenland. G. Brit. S. tomentosum (Fr.) Th. Fr. (D. B., p. 200, Sler. torn, and var. alpinum Laur.). Greenland. G. Brit. GYROPHORACE.E. (Gyrophara). Gyrophora. G. arctica Ach. (D. B., p. 205, G. hyperborea v. arctica Ach.). Greenland. G. Brit. G. cylindrica L. (D. B., p. 206). Greenland. G. erosa Web. (D. B., p. 205). Greenland. G. Brit. G. hyperborea Ach. (D. B., p. 205). Greenland. G. Brit. G. murina D C (D. B., p. 206). G. Brit. G. polyphylla L. (D. B., p. 206). Greenland. G. Brit. G. proboscidea L. with var. deplicans (D. B., p. 205). Greenland. G. Brit. G. vellea L. (D. B., p. 206). Greenland. G. Brit. 120 OLAF C.ALL0E ACAROSPOUACEJ:. (Acarospora, Biatorella). Acarospora. Ac. discreta (Ach.) Th. Fr. Pebbles and firm rock near Husavik. X. Ireland, O. (ialloe, 1913. Ne\v to Iceland. Ac. fuscata (Schrad.) Th. Fr. (D. B., p. 212, Ac. fuse. v. rufescens). Not found in Greenland. G. Brit. Ac. Heppii (Naeg.) Koerb. On basalt, Seydisfjord in K. Iceland; on lava, Havnefjord in S\V. Iceland; O. Gall0e, 1913. New to Iceland. Biatorella. B. Morio Flk. with var. pallescens. (D. B., p. 218). Greenland. G. Brit. EPHEBACEJ: (Ephebe, Polychidium). Ephebe. E. pubescens L. (D. B., p. 202). G. Brit. Polychidium. P. muscicola Sw. (1). B., p. 206). Not found in Greenland. G. Brit. LICHINACE^E. (Lichina). Lichina. L. confinis O. F. Mullcr (I). B., p. 202). Greenland. G. Brit. COLLEMACE.E. (Collema, Leptogiuni). Collema. C. crispum L. (1). B., p. 206). Not found in Greenland. G. Brit. C. flaccidum Ach. (D. B., p. 206, Synechoblastus). Greenland. G. Brit. LICHKNOLOGY OF ICELAND 121 C. nigrescens L. (D. B., p. 200, Synechoblastus). Not found in Greenland. G. Brit. C. pulposum Bernh. (D. B., p. 206). Greenland. G. Brit. C. verrucaeforme L. (D. B., p. 206). Not found in Greenland. Leptogium. L. lacerum Sw. (with v. pulvinatum Ach.) (D. B., p. 206). Greenland. G. Brit. L. (Collemodium) plicatile Ach. On basalt, SeyiMsfjord, (). Galloe, 1913. New to Iceland. L. scotinum Ach. (D. B., p. 206). Greenland. G. Brit. PANNARIACE.E. (Massalongia, Placynthium, Pannaria, Psoroma). Massalongia. M. carnosa (Dicks.) Koerb. Almannagja near Thingvellir, SW. Iceland, O. Gall0e, 1913. New to Iceland. Placynthium. P. delicatulum Th. Fr. (D. B., p. 207, Lecotheciuni). Not found in Greenland. G. Brit. P. nigrum Huds. (D. B., p. 207, Lecothecium). G. Brit. Pannaria. P. brunnea Nyl. (D. B., p. 207). Greenland. G. Brit. P. elaeina Wahlenbg. (D. B., p. 207). Not found in Greenland. P. granatina Sommerf. (D. B., p. 207). Greenland. P. Hookeri Sm. (D. B., p. 207). Greenland. G. Brit. P. lepidiota Sommerf. (D. B., p. 207). Greenland. G. Brit. P. microphylla Nyl. On earth near the summit of the mountain of "Sulur" (Ofjord in N.Iceland), O. Galloe, 1913, and on the mountains in the same place, east of the fjord, idem, 1913. New to Iceland. P. triptophylla Ach. (D. B., p. 207). Greenland. G. Brit. 122 OLAF GALL0E Psoroma. P. (Lecanora) Hypnorum (HoiTm.) Ach. (D. B., p. 209, Squamaria). Greenland. G. Brit. STICTACE.E. (Sticta). Sticta. St. scrobiculata Scop. (D. B., p. 203). Greenland. G. Brit. PELTIGERACE^E. (Nephroma, Peltigera, Solorina). Nephroma. N. arcticum L. (D. B., p. 203). Greenland. N. expallidum Nyl. (D. B., p. 203). Greenland. N. laevigatum v. parile Ach. (D. B., p. 203). Greenland. G. Brit. N. tomentosum HotTm. (D. B., p. 203). Greenland. G. Brit. Peltigera. P. aphtosa L. (D. B., p. 202. Greenland. G. Brit. P. canina (L.) Fr. (D. B., p. 202). Greenland. G. Brit. P. horizontalis L. Kmpetrum-hcath, Seydisfjord, O. Galloe, 1913. New to Iceland. P. lepidophora Nyl. On volcanic tuff near Ljosavatn farm, N. Iceland; heaths near Einar- sta^ir, N. Iceland; heath near M\valn, N. Iceland; mountain-heath near Husavik, N. Iceland; mountain-heath near (") fjord, N. Iceland. O. Galloe, 1913. New to Iceland. P. malacea (Ach.) Fr. (D. B., p. 202). Greenland. G. Brit. P. polydactyla f. collina Ach. (D. B., p. 202). Greenland. G. Brit. P. rufescens Fr. (I). B., p. 202). Greenland. G. Brit. P. venosa (L.) Hottni. (D. B., p. 203). Greenland. G. Brit. LICHENOLOGY OF ICELAND Solorina. S. bispora Nyl. (I). B., p. 203). Greenland. G. Brit. S. crocea Ach. (D. B.), p. 203). Greenland. G. Brit. S. saccata L. (I). B., p. 203). Greenland. G. Brit. PERTUSARIACE.E. (Pertusaria). Pertusaria. P. communis DC. (D. B., p. 211). Not found in Greenland. G. Brit. P. coriacea Th. Fr. (D. B., p. 211). Not found in Greenland. P. corallina (L.) Am. On lava, Havnefjord in SW. Iceland, O. Gallae, 1913. New to Iceland. P. dactylina Ach. (D. B., p. 211). G. Brit. P. oculata Dicks. (D. B., p- 210, Lecanora). Greenland. G. Brit. P. rhodoleuca Th. Fr. (D. B., p. 211). Not found in Greenland. P. xanthostoma (Sommerf.) Fr. (D. B., p. 211). Not found in Greenland. G. Brit. LECANORACE^E. (Haematomma, Lecania, Lecanora). Haematomma. H. coccineum (Dicks.) Koerb. On lava near Havnefjord, SW. Iceland, O. Gall0e, 1913. New to Iceland. H. ventosum L. (D. B., p. 211, Lecania). Greenland. G. Brit. Lecania. L. athroocarpa (Dub.) Nyl. (D. B., p. 211). Not found in Greenland. G. Brit. L. cyrtella Ach. (D. B., p. 211). Not found in Greenland. G. Brit. Lecanora. L. albescens v. dispersa Pers. (D. B., p. 210). Not found in Greenland. G. Brit. 1 2 1 OLAF GALL0K L. alphoplaca Wahlenbg. (D. B., p. 209, Squamaria). Greenland. G. Brit. L. alpina Sommerf. On Liparite, Hlitiarfjall near Mvvaln, N. Iceland: erratic blocks on the mountains east of Ofjord; on stones in Almannaj;'i, S\V. Iceland. O. Galloc, 1913. New to Iceland. L. atra (Huds.) Ach. (D. B., p. 210). (ireenland. G. Hrit. L. atriseda Fr. (D. B., p. 210). Not found in Greenland. G. Brit. L. atrosulphurea (Wahlenbg.) Ach. (D. B., p. 210, L. varia.' forma). L. badia (Pers.) Th. Fr. (D. B., p. 210). Greenland. G. Brit. L. calcarea (L.) Sommerf. On basalt, Reydarfjord in E. Iceland, O. Gall0e, 1913. New to Iceland. L. cartilaginea Westr. (D. B., p. 208, Squamaria). Not found in Greenland. G. Brit. L. castanea (Hepp.) Th. Fr. (D. B., p. 210). Not found in Greenland. L. chrysoleuca Sm. (D. B., p. 209, Squamaria) f. rubina Vill. and melanophthalma Nyl. Greenland. G. Brit. L. cinerea (L.) Sommerf. (D. B., p. 210). Greenland. G. Brit. L. cinereo-rufescens Dicks. (D. B., p. 211). Greenland. G. Brit. L. coarctata v. ornata Sommerf. (D. B., p. 210). G. Brit. L. frustulosa (Dicks.) Koerb. (D. B., p. 209). (ireenland. G. Brit. L. gelida (L.) Ach. (D. B., p. 20r. (D. B., p .211) with var. parella L and Upsaliensis L. (ireenland. G. Brit. L. poliophaea Wahlenbg. (I). B., p. 209). G. Bril. L. polytropa Khrh. (D. B., p. 210, L. variae forma). LICHENOLOGY OK ICELAND 125 L. protuberans Sommerf. v. carneopallida Nyl. (D. B., p. 210). Greenland. G. Brit. L. saxicola (Poll.) Slenh. (1). B., p. 209, Squamaria). Greenland. G. Brit. L. sordida (Pcrs.) Th. Fr. v. glaucoma (Hoflm.) Th. Fr. (D. B., p 209). G. Bril. L. straminea Wahlenhg. (D. B., p. 209, Squamaria). Greenland. L. subfusca (L.) Ach. (v. coilocarpa Ach., Hypnorum (Wulf.) Schaer., glabrata Ach., rugosa Pers., atrynea Ach.) (D. B., p. 209), Greenland. G. Brit. L. tartarea L. (D. B., p. 211). Greenland. G. Brit. L. varia (Ehrh.) Nyl. (D. B., p. 210, with var. symmicta Ach., po- lytropa Ehrh., intricata Schrad., atrosulphurea Wahlenhg., leptacina Sommerf.). Greenland. G. Brit. L. verrucosa Ach. (D. B., p. 211). Greenland. G. Brit. PARMELIACE.E. (Cetraria, Parmelia). Cetraria. C. aculeata Fr. (D. B., p. 200). Greenland. G. Brit. C. cucullata Bell. (D. B., p. 204). Greenland. G. Brit. C. Fahlunensis (L.) Schaer. (D. B., p. 204). Greenland. C. hiascens (Fr.) Th. Fr. On earth on mountains near Husavik, N. Iceland ; on mountains east of Ofjord, O. Gallee, 1913. New to Iceland. C. Islandica Ach. with var. crispa Ach. and Delisei Bory. (D. B., p. 203). Greenland. G. Brit. C. nivalis (L.) Ach. (D. B., p. 203). Greenland. G. Brit. C. saepincola (Ehrh.) Ach. with v. chlorophylla Humb. (D. B., p. 204). Greenland. G. Brit. Parmelia. P. alpicola Th. Fr. (D. B., p. 205). Greenland. G. Brit. 12C) "LAP GALL0E P. ambigua Ach. (D. B., p. 204). Greenland. G. Brit. P. encausta Sm. (D. B., p. 204, P. enc. v. intestiniformis Vill.). Greenland, (i. Brit. P. incurva Pers. (D. B., p. 204). Greenland. G. Brit. P. lanata (L.) Walbr. (D. B., p. 204). Greenland. G. Brit. P. olivacea L. (I). B., p. 204, f. prolixa, fuliginosa, sorediata, aspidota). Greenland. G. Brit. P. physodes L. (D. B., p. 204). Greenland. G. Brit. P. saxatilis L. with v. omphalodes (L.) Fr. (D. B., p. 204). Greenland. G. Brit. USNEACE.E. (Alectoria, Evernia, Ramalina, Thamnolia, Usnea). Alectoria. A. divergens Ach. (I). B., p. 200). G. Brit. A. jubata L. (D. B., p. 200, Bryopogon). Greenland. G. Brit. A. nigricans Nyl. (D. B., p. 200). Greenland G. Brit. A. ochroleuca Nyl. (D. B., p. 200, with v. cincinnata Fr.). Evernia. E. furfuracea L. (D. B., p. 204). G. Brit. Ramalina. R. scopulorum Retz (D. B., p. 200, "inclusis cuspidata Nyl. el formis inter fnrinaceam L. et R. scop, intermediis"). R. subfarinacea Nyl. (D. B., p. 200, probably included in R. scop.). Thamnolia. Th. vermicularis Scha-r. (D. B., p. 202). Greenland. G. Brit. Usnea. U. melaxantha Ach (D. B., p. 200). Greenland. LICHENOLOGY OF ICELAND 127 CALOPLACACE.E. (Caloplaca). Caloplaca. C. aurantiaca Lightf. (D. B., p. 208, Placodium). G. Brit. C. cerina (Ehrh.) Th. Fr. (D. B., p. 207, Placodium cer. f. stilli- cidiorum). Greenland. G. Brit. C. citrina Adi. (D. B., p. 208, Placodium). (1. Brit. C. diphyes Nyl. (I). B., p. 208, Placodium). Not found in Greenland. C. elegans (Link) Th. Fr. (D. B., p. 205, Xanthoria). Greenland. G. Brit. C. ferruginea (Huds.) Th. Fr. v. obscura Th. Fr. (D. B., p. 208, Placodium). Greenland. G. Brit. C. Jungermanniae (Vahl) Th. Fr. (D. B., p. 208, Placodium Jung. and var. leucoraeum). Greenland. C. murorum Hoffm. with var. miniatum Ach. and obliteratum Pers. (D. B., p. 207, Placodium). C. nivale Koerb. (D. B., p. 208, Placodium). G. Brit. C. obscurella Lahm. (D. B., p. 208, Placodium). Not found in Greenland. C. pyracea (Ach.) Th. Fr. (D. B., p. 208, Placodium). Greenland. G. Brit. C. tetraspora Nyl. (D. B., p. 208, Placodium). Not found in Greenland. C. vitellina (Ehrh.) Th. Fr. (D. B., p. 207, Placodium). Greenland. G. Brit. THELOSCHISTACE.E. (Xanthoria). Xanthoria. X. lychnea (Ach.) Th. Fr. (D. B., p. 205, X. par. v. lychnea). Greenland. G. Brit. X. parietina L. (D. B., p. 205). Greenland. G. Brit. 128 01. Al- (1ALL0E BUELLIACE/E. (Buellia, Rinodina). Buellia. B. aethalea (Ach.) Th. Fr. Palagonite-tuff near Husavik, N. Iceland, (). (ialloc, 1913. New to Iceland. B. atroalba Ach. (D. B., p. 218, with var. chlorospora Nyl.). B. badia Koerb. (D. B., p. 217). Not found in (ireenland. B. coniops Wuhlenbg. (D. B., p. 217). (ireenland. G. Brit. B. leptocline Plot. (D. B., p. 217). Not found in (ireenland. (i. Brit. B. myriocarpa (DC.) Mudd. (D. B., p. 217). (ireenland. (i. Brit. B. parasema (Ach.) Th. Fr. var. muscorum (Schaer.) Th. Fr., papil- lata (Sm.) Th. Fr., triphragmia (Nyl.) Th. Fr., albocincta (D. B., p. 217). (ireenland. (i. Brit. B. scabrosa Koerb. (D. B., p. 212, Karschia). G. Brit. B. stellulata Tayl. (D. B., p. 218). (ireenland. (i. Brit. B. tesserata Koerb. Cliffs, Sey&isfjord in E. Iceland, O. (iallee, 1913. New to Iceland. B. vilis Th. Fr. (D. B., p. 217). Not found in (ireenland. Rinodina. R. Conradi Koerb. (D. B., p. 212, Urceolaria). (ireenland. (1. Brit. R. mniaroea (Ach.) Th. Fr. v. cinnamomea Th. Fr. (D. B., p. 212, Urceolaria). R. sophodes Ach. (D. B., p. 212, Urceolaria soph, and var. con- fragosa Ach., v. exigua Ach.). (ireenland. (i. Brit. R. turfacea Wahlenbg. (D. B., p. 212, Urceolaria). (ireenland. PHYSCIACE^E. (Physcia). Physcia. P. aipolia Nyl. On basalt, SeycMsfjord in E. Iceland, O. Galloc, 1913. New to Iceland. UCHENOLOGY OF ICELAND 129 P. aquila Ach. (D. B., p. 205). G. Brit. P. caesia (Hottrn.) Nyl. (D. B., p. 205, P. stellaris v. caesia). Greenland. G. Brit. P. ciliaris L. (D. B., p. 205, P. cil. and v. scopulorum Nyl.). Greenland. G. Brit. P. pulverulenta Nyl. v. muscigena Nyl. (D. B., p. 205). Greenland. G. Brit. P. obscura (Ehrh.) Nyl. (D. B., p. 205). Greenland. G. Brit. P. stellaris L. (D. B., p. 205). Greenland. G. Brit. The Botany of Iceland. Vol II. II. THE MEANS OF PROPAGATION AND DIS- PERSAL OF THE ICELAND LICHENS. Ater having considered, in the above, the composition of the Flora, the next point to be investigated is, by which means of propagation we can imagine that the species have been dispersed over the island, and have immigrated from the surrounding coun- tries into Iceland, and vice versa. Lichens are propagated by Ascospores, Pycnoconidia, Sored ia, and detached portions of thallus. Ascopores must be assumed to be the original means of pro- pagation, which, as we know', has been handed down directly from the prototypes of the lichens, the Ascomycetes. Those lichens which still stand on a low, primitive phylogenetic stage, viz. the Crusta- ceous Lichens, have still, almost all, as a rule more or less numerous apothecia, usually with numerous well-developed spores. In the synoptic list of the chief biological conditions of the lichens of Iceland (see below) it will be seen that all the crustaceous lichens have been, and as a rule will be, found with apothecia. Among the Foliaceous Lichens there are several which often occur in great abundance, but are nevertheless rarely found with apothecia. This is for instance the case with Cetraria acnleata, C. cucnllatd, C. hiascens, C. niualis, Nephroma spp., some Pelliyera spp., Physcia pnl- vernlenta \. innscigena, and perhaps a few other species. As will be seen, it is all the leaf-shaped earth-lichens which can undoubtedly be propagated by detached portions of thallus, which; when the plant is in a dry condition, are widely dispersed by the wind, or perhaps also, in part, by animals; but no thorough investigations are to hand as regards this point. What has been said of the foli- aceous lichens is also frequently the case among the Fruticose Lichens, namely, that apothecia are rare, while other means of LICHENOLOGY OF ICELAND 131 propagation, soredia or detached portions of thallus, are extremely common. This is the case for instance with Alectoria and several Cladonia spp. Here there undoubtedly also exists a certain correla- tion between these means of propagation, vegetative means of pro- pagation in several species being of far greater importance for the dispersal of the species, than ascospores. This phenomenon of vege- tative propagation is known from several places; thus in Denmark Cladonia rangiferina is sterile as a rule, and is most frequently pro- pagated there by detached portions of podetia, and the same is the case with Cladonia nncialis, etc.: this circumstance, however, has been^exhaustively discussed by me previously (Gall0e, 1913, p. 41, and under the different species in the same paper). As regards Thamnolia vermicularis, it never forms apothecia. As to how the ascospores escape from the ascus and their mode of dispersal, are but little known. There is much which goes to show that in the majority of species the spores are dry bodies, which are carried away by the wind and thereby dispersed. But it is just possible that in some of the species they are sticky, and require other means of dispersal. Pycnoconidia. At present very little is known as regards the extent to which pycnoconidia occur among the Crustaceous, Foliaceous and Fruticose Lichens, nor is it known what role they play as regards propagation. They have been regarded both as male reproductive cells, and as vegetative means of propagation. In some cases, investigators have succeeded in producing the lichen-thallus by bringing together pycnoconidia and gonidia in a pure culture, that is, have succeeded in propagating lichens vegetatively by pycno- conidia; this, however, does not necessarily compel us to regard the pycnoconidia of all species as vegetative means of propagation. To regard pycnoconidia as male reproductive cells, is perhaps more disputable; their importance as such has not at any rate been proved; their entire biological importance is consequently rather problematic. To make investigations regarding this point will, no doubt, well repay the trouble. According to what has just been said, nothing can be stated at the present time as to whether there exists any correlation between the occurrence of pycnoconidia and the occurrence or absence, respectively, of other means of propagation. Soredia, as is well-known, are small bodies which consist partly of hyphae and partly of gonidia, and are formed sometimes in quite accidental places the on thallus, sometimes in fairly well- 9* 132 OLAF GALL0E defined patches, the so-called sorals. They have been regarded partly as a peculiar means of propagation produced recently, from a phylogenetic point of view, in the more differentiated (little pri- mitive) species, partly as a pathological phenomenon, due to the fact that the gonidia, with abundant moisture, grow "wild," and burst the outer morphological frame, which the lichen-hyphae would give to each species, as the one characteristic to the species. That soredia-production may be pathological, and in many cases is exclusively so, I lake for granted, but I am equally convinced that it is not so in all cases. Because in that case, Cladonia pityrea, for instance, which is always sorediiferous, must be regarded as a pathologically deformed form of another species, which, under normal conditions, has a quite different appearance. Something to that effect we were obliged to assume as regards the many other lichens, entirely or partially covered with soredia, which occur all over the world. But that such a view cannot be maintained, I consider as certain. It must, however, be pointed out that cultural experiments alone, can decide this question, and such experiments have not been made. It would be necessary, for instance to cultivate soredia in a place drier than that where the sorediiferous species in question has been collected, and try if such a culture would produce a totally different, non-sorediiferous individual, which might, perhaps, prove to be a species already known. Whether soredia-production is a pathological or a normal feature, at all events there is no doubt that it is promoted by dampness. Soredia have also been regarded as a normal means of pro- pagation in the species in question, and there is no reason what- ever to doubt that they may be of this importance. In itself there is nothing to prevent soredia-production from being in some cases pathological, in others normal. In the Crustaceous Lichens of Iceland soredia-production does not appear to be a common phenomenon. I did not find it widely distributed. Lepraria appears to be much less widely dis- tributed in Iceland than in Denmark. Among the Folia ceous Lichens, soredia-production is met with in Cetraria saepincola v. chlorophylla, Parmelia ambigua, incnrva, physodes, saxatilis, stygia, Physcia ccesia, obscura and stellaris. Among the Fruticose Lichens it is found in several Cladonia species (Floerkeana, pityrea, fimbriata, etc.), Kamalina subfarinacea and Usnea mela.vantha. In several of these species soredia appear LICHENOLOGY OF ICELAND 133 to be a very common means of propagation, and to occur where apothecia are rare, or not very frequent, (e. g. Cladonia fimbriata, Ramalina subfarinacea and Usnea melaxantha). The soredia are dis- persed by the wind, or perhaps by adhering to the hair of animals. Detached portions of thallus as a means of propagation are not known to occur with any certainty in a single Crustaceous Lichen. It is probable that this happens in the above-mentioned Foliaceous Lichens. In the Fruticose Lichens it has been demonstrated with certainty in several earth-lichens (Cladonia, etc., for instance Cladonia rangiferina, uncialis, rangiformis, etc.). In 1913 I fully mentioned and figured it in several species. It appears to be a very important and widely distributed means of propagation in several species, and largely replaces propagation by ascospores, which in such species usually occur rather rarely. Dispersal takes place no doubt both by the agency of the wind and of animals. If we consider the way in which lichens may be assumed to have been dispersed in Iceland itself, we must understand clearly that ascospores, pycnoconidia, soredia, and detached por- tions of thallus are, as far as we know at present, generally dis- persed by the agency of the wind. But animals also no doubt, more or less, play their part in it. It may be regarded as certain that almost all animals that wander about in Iceland occasionally get lichen-spores, portions of thallus, etc. attached to them. Sheep that roam about almost everywhere, undoubtedly play no small role as disseminators, and the same, I dare say, applies to the majority of the other terrestrial animals, wild as well as tame. How far means of propagation such as ascospores and pycnoconidia, after having passed through the digestive organs of lichen-eating animals (sheep and reindeer), retain their power of germination, is not known in any single instance. Here, as everywhere in the lichen-biology, we stand at the present time just at the stage of asking questions, with- out as yet having got very many of them answered, because lichen- ologists do not, on the whole, occupy themselves with biological problems. But in a general way it may be said that species which play any essential part as articles of food for animals, namely the larger shrub-like earth-lichens, are generally little dispersed by asco- spores, for they bear fruit rather sparingly, as mentioned above. l.'M 01. AI (i.M.I.OK Species such as Cladonia ranyiferma, Alectoria ocliroleuca, Celrnria (icnleata, and Alectoria nigricans are undoubtedly far more frequently propagated by detached portions of thallus, some carried away by the wind, and others adhering to the body of animals. That portions of thallus should be able to pass through the digestive organs of animals uninjured, is a priori improbable, if such were the case, they would be rather useless as fodder! Any possibility of such dispersal by means of herbivorous animals, is thus scarcely possible. But water, also, plays a part in the dispersal of lichens. By the agency of water, the submerged Verrucaria spp. which live along the coasts, are undoubtedly dispersed. Then it is probable that the lichens which occur by water-falls, part of which live washed by the falling water (for instance Staurothele clopima), are dispersed by the downward-flowing water. If we now consider the agencies which play or have played a part in the exchange of lichen-species with the surround- ing countries, we must, as in the case of dispersal in Iceland itself, point out three different agencies: wind, water and animals. The lichens which may be assumed to have immigrated, (re- spectively emigrated,) by the agency of the wind, are firstly all those that propagate by ascospores, consequently, practically all the crustaceous lichens, at any rate, by far the greater part of the species (about 65 %); then next, the majority of the foliaceous lichens, possibly all of them (there are altogether about 21 % of them); and lastly some fruticose lichens. As regards the latter, however, it must be taken for granted, that at least Thamnolia vermicularis did not migrate in the form of spores, as it never bears fruit. Some of the species have probably also migrated by means of pycnoconidia, but as the occurrence of the latter in the species is very incompletely known, and as their importance as a means of propagation may be disputed, it is not possible to form any opinion as to what importance they are of or have been, in respect to immigration. Lastly, some species have migrated as soredia. As mentioned above the soredium is not a very common means of propagation in the Icelandic species; in the crustaceous lichens it is extremely rare. I am not prepared to state with any certainty in how many I.IC.HENOLOGY OF ICELAND 135 species it occurs, but if it be found in about 20 species, that is no doubt all, and does not form even one-tenth of the species. The chief means of propagation of crustaceous lichens is, as we know, ascopores. In the foliaceous lichens it has been found in the species about 9 mentioned above, that is to say, in about one-sixth of the total number of species. In how many species of fructicose lichens it has been found, cannot be stated with any certainty, but doubtless, the number does not greatly exceed that of the foliaceous species. Whether any immigration has taken place by means of de- tached portions of thallus which have been conveyed by the wind, it is impossible to decide. It has been mentioned above that this mode of dispersal plays a considerable part within the boundaries of the country, with regard to many of the fruticose and foliaceous lichens. But whether portions of thallus, capable of germination, are really transported through the air from the surrounding countries, cannot, of course, be known, but the possibility is scarcely pre- cluded. Judging from the above, the role which we must assume that the wind has played in the immigration and emigration of Iceland's species, is thus very considerable, as all the crustaceous lichens and the majority perhaps even all - - of the fructicose and foliaceous lichens have such means of dispersal (ascospores, pycnocodia, soredia and detached pieces of thallus) as justify us in believing that the wind in particular has transported them to the country. Water has played a far less considerable part as a means of dispersal, in fact, it can be assumed only with regard to the few submerged Verrncaria spp., and the emergent V. manra, that they have immigrated by this means. They occur doubtless, over nearly the whole of the Arctic, and over great parts of the adjoining climate- areas, on cliffs out in the sea. They are common on the coasts of Greenland, Iceland, Norway, the Fseroes, Denmark and Great Bri- tain, consequently both in Arctic and in temperate regions. They constitute altogether not above 2 3 % of the flora of Iceland. What importance animals have had as regards immigration is quite unknown. Here again it must suffice us to frame questions which will, perhaps, in the future, be taken up and answered by others. Primarily it may be supposed that birds of passage which migrate backwards and forwards between Iceland and milder regions, 136 OLA I (,AI,L0K according to the season of the year, may transport lichen- u germs" capable of germination, to Iceland, but nothing is known regarding this point. At the present time it is not even possible to procure a list of the lichens, which grow on cliffs inhabited by sea-fowl in both Scotland and Iceland, from which an opinion could be formed as to how far such transport between these countries is probable. But even if there were a distinct agreement of flora between such localities, that would by no means prove that the transport had been made only by birds. We should be justified in assuming that the lichen-"germs" have been carried along by wind or perhaps water and that this agreement is due to the similarity of the substratum, i. e. one especially manured by birds, as regards the solution of this question, there is scarcely any other way out of the difficulty, than by a direct investigation of what migrating birds can possibly carry of lichen spores and parts along with them, adhering to their feet or to other parts of their bodies, when they arrive at the country in spring; but this will be a very minute and difficult investigation. But whatever the result may be at which we arrive by that method, it will not be able to modify, to any degree w r orth men- tioning, the view that all other means of migration taken together, scarcely play so great a part in the immigration, as does transport by wind. Even if we imagined all other means eliminated, the flora would, in all probability, have acquired the same essential composition, as that now existing, by the agency of the wind alone; all our knowledge of the means of dispersal of the species is sug- gestive of this. But this does not exclude the possibility that many species are transported into the country in more ways than one, for instance both by birds and by wind. It is only with regard to the few submerged species, that the wind has probably played no part at all. Here I believe ocean- currents, and perhaps sea-fowl, have been the transporting agencies. III. THE BIOLOGY OF THE LICHENS OF ICELAND. TICHENS may be divided into the following biological types : -Lj Bark, (Epiphyllous), Earth, Rock, (Parasitic) and (Sa- prophytic) lichens. The three enclosed in brackets are wanting in Iceland, (but possibly one or other of the last two groups may be found there), and therefore will not be discussed here. With regard to these it will suffice to refer the reader to my treatise "For- beredende Unders0gelser til en almindelig Lichenokologi" (1913). 1. BARK LICHENS. To this group I refer not only those which grow on the bark of trees, but also such as grow on bare wood (telegraph poles, sur- faces of wooden houses, etc.). These substrata have practically not been investigated as regards lichen-biology, whilst their anatomy has been investigated long ago. The chemical properties of the bark and their importance to lichens, are as yet very superficially known. The bark always con- tains organic substances (suberin, cellulose, tannin, resin, etc.), in- organic salts, etc. Besides, it may be taken for granted, that the outside layer of bark is generally more decomposed than are the inner ones. That the bark differs distinctly as a substratum ac- cording to whether it is young or old, is evident from the investi- gations which Lotsy (1890) and I myself have made, regarding the immigration-history of the lichens on bark. These investigations have shown that the pioneer vegetation always consists of certain crustaceous lichens, and is not replaced until later by the permanent vegetation. I have no certain knowledge of this immigration-history as regards Iceland, but I have reason to believe that the rule men- tioned above also holds good there. Judging from what is known, the reason for this vegetation order is a fairly similar process of decomposition in the different kinds of bark, for barks even very different physically (smooth and l.'JN OLA I (i.\l.I.0K scaly) show quite analogous features in the development-history of the vegetation. I am not aware of the existence of any thorough chemical in- vestigation of the different kinds of hark, nor do I believe that such exists, except perhaps as regards the officinal barks. Neither have, as yet, the physical conditions of bark been investi- gated. We can, upon a superficial survey, immediately distinguish between the two, well-known groups, smooth bark and scaly bark. They are easily distinguished from each other. I have known, as a general fact, that the systematic species of the tree, is of no importance to the biological types which settle down on its bark, as crustaceous, foliaceous and fruticose lichens may be found on all of them. Which of these types is to dominate the vegetation when it is fully developed, depends on the degree of light to which the tree is exposed, and other meteorological cir- cumstances, as I have shown in my \vork on "Danske Licheners 0kologr (1908). On the other hand, the floristic composition of the vegetation varies essentially, according to the systematic species of the tree. Experience shows that certain lichens occur by preference on cer- tain species of trees, (Usnea spp. on coniferous trees, etc.). It is possible that, by more thorough investigations, we shall also be able to find fixed rules for this association, but as yet nothing is known regarding this point. At present we must be content with the lists of lichens compiled for each species of tree, as has been done in "Danske Likeners 0kologi," and as regards Iceland, when discussing the lichens of the Birch later on in this paper. Wood. Many species which occur most frequently on bark, may occasionally be found on bare wood. Wood is chemically closely related to bark, and the lichens which occur on it can, as a matter of course, be classified among the bark lichens. It must, however, be mentioned with respect to the growth-tensions which occur in the bark during the growth of the tree, and which are inclined to stretch the crust-shaped lichens into elliptical or oval crusts, with the main axis of the ellipse at right-angles to the longi- tudinal axis of the tree, that these, of course, will not be fonnd in dead wood. There, on the contrary, the crustaceous lichens grow parallel with the "fibres," i. e. parallel with the longitudinal axis of the stem, hence the reason why lichen-crusts which grow un- influenced by neighbours and competitors, are very often oval or UCHKNOLOOY <)!' ICKLANI) 139 elliptic in shape, with their main axis parallel with the longitudinal axis of the tree. In Iceland there occurs rather a common wood -substratum, namely the old decomposed walls of the wooden houses. On such walls I found the following common species: Buellia myriocarpa. Caloplaca vitellina. Lecanora Hageni. pyracea. varia. Physcia obscura. subfusca. Bark-lichens may be divided into Crustaceous, Foliaceous and Fruticose lichens. Of Crustaceous bark-lichens there are two different types, hypophlceodal and epiphlceodal. The hy pophloeodal crustaceous-lichens (numerous Graphidece, etc.) have, as regards their attachment to the substratum, been long ago investigated very thoroughly by Lindau (1895), to whose treatise I refer the reader. Their thallus lives in the interior of the bark of trees, covered by its cells, which afford the lichen protection against evaporation. According to Lindau their hyphse appear to be quite unable to dissolve the cellulose of the bark, so they probably live on its de- composition-products. They themselves, however, contribute towards decomposition by bursting asunder the cells by the tension of their growth, whereby air and water gain access to the bark. The thallus is otherwise homoiomerous in structure in several of the species, in others distinctly heteromerous ; consequently, on the whole, very primitive, and only slightly removed from the purely mycelial fungal prototypes. The hypophlojodal crustaceous-lichens stand extremely low both in respect to morphology and anatomy, and as regards their capacity for competition with other plants. They live exclusively on the bark of trees and have no analogues among the earth-lichens and only a fe\v (and these even very disputable,) among the rock- lichens with endolithic thallus. Only where other bark-lichens are absent for various reasons, may these occur, but if the conditions are favourable to fruticose and foliaceous lichens, they are imme- diately expelled by these. They are most frequent on smooth bark the numerous smooth-barked trees of the tropics house an abun- dance of them - and they remain there so long as the bark is not decomposed enough to house other, more pretentious types. 140 OLA I (',. \LL0E The course of development in the decomposition of the hark, and the consequent change of vegetation from hypophkeodal to epi- phla-odal and other bark lichens, may be studied on almost every old tree. Ho\v many of Iceland's bark lichens are hypophlcoodal, has not been investigated. The epiphlu-odal crustaceous-lichens are fastened to the sub- stratum like the hypophloeodal; they have been investigated by Lindau (1895). They have a hyphal tissue that sinks into the bark and ruptures the cells of the bark, but is not able to dissolve their cellulose. The gonidia-containing part of the thallus is on the sur- face of the bark, hence their name and is more or less dis- tinctly covered with a cortex, showing all transitions between species with the thinnest and the thickest cortex. In several crustaceous lichens soredia are formed which can propagate the plant, for instance in the Variolaria spp. This mode of propagation indicates a higher morphological stage than that of the hypophlceodals, in which anything like it appears to be rare. With regard to competitive capacity, in most of the habitats the epiphlceodals stand above the hypophlu'odals, but they generally appear to need a more advanced stage of decomposition of the bark, than do the latter, so that they frequently succeed to them as the bark gradually gets older. It is possible that they also require more light. Of crustaceous bark-lichens Iceland has the following: Arthonia proximella Nyl. punctiformis Ach. Arthopyrenia analcpta Ach. grisea Schleich. Hacidia abbrevians Nyl. arceutina Ach. atrosanguinea Schaer. Beckhausii Koerb. rubella Ehrh. sphaeroides. Bucllia myriocarpa (D C) Mudd. parascma (Ach.) Th. Fr. Caloplnca cerina (Ehrh.) Th. Fr. citrina Ach. ferruginea (Huds.) Th. Fr. Diploschistes scruposa L. Lecania athroocarpa (Dub.) Nyl. Lecania cyrtella Ach. Lecanora atra (Huds.) Ach. Hageni (Ach.) Koerb. pallescens (L.) Schaer. protuberans Sm. subfusca (L.) Ach. tartarea L. varia (Ehrh.) Nyl. Lecidea crustulata (Ach.) Koerb. Diapensias Th. Fr. elaeochroma (Ach.) Th. Fr. erytrophoea Flk. fuscescens Sm. helvola (Koerb. Th. Fr. Nylanderi Anzi. Tornoensis Nyl. Lepraria. L1CHENOLOGY OF ICELAND 141 Microthelia micula Plot. Pertusaria xanthostoma (Sm.) Fr. Pertusaria communis D C. Rinodina sophodes Ach. The Foliaceous bark-lichens appear to be far richer and more varied in structure, and probably comprise very different types, which have not yet, however, been investigated from a biological point of view With regard to this point, it will suffice for me to draw attention to the striking difference between such species as are adpressed to the substratum (Physcia pulveralenta), the surface of which the lichen follows along all its irregularities; and on the other hand Parmelia physodes, the greater part of which rises into the air, and lastly Evernia Prunastri, which hangs down in tufts from trunks and branches. The thallus of the foliaceous lichens is dorsiventral, is covered by a cortex, and has rhizines on its under surface. The rhizines attach the lichen to the substratum in the way described by Lin- dau, for, on coming into contact with the bark, they spread out flat over the substratum and, when the bark is well decomposed, send hyphae down into its cracks for further attachment. The rhi- zines are unable to dissolve the cellulose, but it may be presumed that they absorb the salts set free by the decomposition of the bark. The gonidia-containing thallus itself is, as is well-known, in- dented in various ways, and grows centrifugally over the substratum, for which reason it often dies away in the centre, a fact commonly observed, especially in Parmelia saxatilis and Sticta pnlmonacea. The edge of the thallus gradually forms new rhizines on the side turned downwards. The gonidia are situated just below the cortical layer of the morphological upper-surface. Propagation takes place by means of spores, possibly by pycnoconidia and soredia, which are extremely common in several species (Parmelia and Evernia spp.). In their competitive capacity the foliaceous lichens stand, in many habitats, far above the crustaceous lichens. They generally require more thoroughly decomposed bark than do the latter, there- fore (with a few exceptions) they do not live on young branches. In addition, they generally demand more light. Consequently, where abundant light and well-decomposed bark are found, the vegetation of the bark of the tree consists of foliaceous lichens, which easily grow over and exterminate the original vegetation of crustaceous lichens. In the birch coppices of Iceland this may be observed here and there on older trunks and branches, especially in parti- 142 OLAF C.ALL0K cularly wind-affected coppices of which the tops of the shoots are dead. The conditions pertaining to propagation in the foliaceous lichens do not appear to differ from those in the crustaceous lichens. Iceland has the following foliaceous bark-lichens : Cetraria ssepincola (Ehrh.) Am. Parmelia olivacea L. r.ollema flaccidum L. physodes L. nigrescens L. saxatilis L. Kvernia furfuracea L. Physcia ciliaris L. Leptogium plicatile Ach. obscura (Ehrh.) Nyl. Ncphroma laevigatum. stcllaris L. tomentosum. Sticta scrobiculata Scop. Pannaria triptophylla Ach. Xanthoria lychnea (Ach.) Th. Fr. Parmelia ambigua Ach. parietina L. Fruticose bark- lichens (Usnea, Ranuilina, Bryopogon) are not found in Iceland, so they will not be discussed more fully here. They are described in my treatise of 1913, pp. 19 et seq. 2. EPIPHYLLOUS LICHENS. are not found in Iceland. They require evergreen leaves as a sub- stratum. These extremely interesting plants received brief mention in my paper of 1913. The chief work on them is Ward's treatise of 1893. 3. EARTH LICHENS. Three types may be distinguished: Crustaceous, Foliaceous and Fruticose lichens, all three of which are found in Iceland. In all Crustaceous earth-lichens there is a distinct de- marcation between that part of the thallus which is buried in the ground (subterranean, hypogaean thallus) and that which rests upon the surface of the ground (epigaean thallus). The subterranean thallus may vary fairly markedly in appearance: it may be com- posed of small, more or less loosely connected grains (Lecidea nli- yiiiosa, L. dlpestris, L. arctica, Gijalecta (jeoica), or it may consist of a homogeneous crust (Bilimbia sabnletorum. Lecidea Diapensicr, etc.), or of small, somewhat scale-like parts coherent at the base (Splnj- ridiuin bijssoides). The biological importance of these forms has not yet been investigated. The gonidia occur sometimes evenly distributed in the whole of the epigaean thallus, sometimes arranged in a definite layer im- mediately beneath the cortex. LICHENOLOGY OF ICELAND 143 The subterranean thallus normally is free of gonidia (barring foreign-gonidia). It may be very strongly developed, and it pushes its way down among the particles of soil, which may gradually become entirely enclosed by its hyphse. I have sometimes observed shapeless enclosed lumps of black humus (Lecidea decolorans, Bi- limbia sabiiletorum (D. Lik. 0., pi. 4, fig. 15), Bacidia citrinella), some- times organic remains with the cell-structure preserved (Lecidea de- colorans), and sometimes grains of mineral matter (Buellia scabrosa). In no case has it been possible to demonstrate whether solution takes place by the agency of the licheh-hyphse. It is almost incom- prehensible that something of this kind should not happen, but it has not been proved. It is possible that what is set free of the enclosed organic remains, or of the mineral grains by purely che- mical decomposition, suffices for the lichens. In some few cases (Lecidea decolorans (I). Lik. 0., pi. 10, fig. 53, c), Pannaria brunnea) I found, enclosed in the subterranean thallus, an undetermined species of green algse. The gonidia were dead and decoloured, but the lichen-hyphae had not sent haustoria into them (nor do they do so as a rule to their normal gonidia). The death of the gonidia was undoubtedly due to contact with the hyphse, and possibly some use had been made of their contents. The whole thing must be regarded as a Cephalodium-formation, a "hypogaean" cephalodium or perhaps a "pseudocephalodium." About the mode of propagation of the crustaceous lichens very little is known. Ascospores, perhaps pycnoconidia, are probably their most common means of propagation, I have not observed soredia or detached portions of thallus in them, as in the fruticose lichens. It is a very interesting fact, that these means of propagation appear to be at any rate rare in the primitive, crustaceous lichens. Crustaceous lichens are very weak in competition with other plants, as these easily cover them over and exterminate them. They are most favourably situated in Iceland, and in other Arctic coun- tries; this will be discussed more fully below. Iceland has the following crustaceous earth-lichens: Bacidia arceutina Ach. Baeomyces byssoides (L.) Th. Fr. caudata Nyl. placophyllum \Vahlenbg. flavo-virescens Dicks. Buellia badia Koerb. herbarum Hepp. parasema (Ach.) Th. Fr. milliaria Fr. scabrosa Koerb. obscurata (Sm.) Th. Fr. Caloplaca cerina (Ehrh.) Th. Fr. squalescens Nyl. Jungermanni3e(Vahl)Th.Fr. 144 01. AF (1ALL0K Caloplaca nivale Kocrb. tetraspora Nyl. vitellina Ehrh.) Th. Fr. Catillaria cumulatu Sm. Jemtlundica Th. Fr. Collema vcrrucaeforme L. pulposum Bernh. Coniocybe furfuracea L. Gyalecta cupularis Khrh. i'oveolaris Ach. Lecanora castanea (Hepp.) Th. Fr. Hageni (Ach.) Koerb. pallescens (L.) Schaer. subfusca (L.) Ach. tartarea L. varia (Ehrh.) Nyl. Lecidea alpestris Sm. arctica Sm. assimilata Nyl. atrorufa Dicks. Berengeriana Mass, crassipes Th. Fr. cuprea Sm. decipiens Ehrh. decolorans Hoffm. elseochroma (Ach.) Th. Fr. 1'usca Schaer. Lecida granulosa (Ehrh.) Schaer. limosa Ach. lurida Sw. neglecta Nyl. rubiformis Wahlenbg. ramulosa Th. Fr. uliginosa Schrad. vernalis (L. Ach. Lepraria. Lopadium f'uscoluteum Dicks. pezizoideum (Ach. Koerb. Massalongia carnosa (Dicks.) Koerb. Microglaena sphinctrinoides Nyl. Pannaria brunnea Nyl. lepidiota Sm. Pertusaria coriacea Th. Fr. dactylina Ach. oculata Dicks. Placynthium delicatulum Th. Fr. Psoroma Hypnorum (Hoffm.) Ach. Rinodina Conradi Koerb. mniaraea (Ach.) Th. Fr. turfacea Wahlenbg. Toninia squalida (Ach.) Nyl. syncomista (Flk.) 'Th. Fr. vesicularis Hoffm. The Folia ceous earth- lie hens may be divided into at least two groups, procumbent and erect. To the procumbent group be- long, e. g. Peltigera (canina, horizontalis, venosa, aphtosa, lepidophora), Solorina (crocea, saccata , bispora) , Physcia (pulverulenta v. mnsci- ycna, stellaris), Dermatocarpon (hepaticum. du'dalenni, cinereum ). To the erect group belong Cetraria (islandica, odontella, ciicullata, ni- valis, glanca, lacnnosa) and some of the species of Collema and Leptogium. It is possible that some of the species may be pro- cumbent under certain circumstances, and erect under others. It is clear that these species differ essentially as regards their competitive capacity against other plants. The erect species must be regarded as the best equipped in that respect, and are also those which are most frequent and most numerous in nature. As is well-known the Cetraria spp. are much more numerous than are any of the pro- cumbent earth-lichens. The Procumbent foliaceous lichens grow cenlrifugally from the centre of the plant, and are provided with scattered bundles of rhixines on their under surface. The rhizines attach themselves LICHENOLOGY OF ICELAND 145 gradually to the substratum, as they come in contact with it. How they attach themselves, and how far they are of any other import- ance than to fix the plant in the substratum, is not known. The thallus itself is always dorsiventral and in some species it dies away in the middle, its single lobes thus becoming isolated. Zukal (1895) has shown that several of the earth-lichens "wander" by a kind of mycelium, which proceeds from their rhizines, and run horizontally below the surface of the ground, forming new 7 thalli here and there, as in Peltigera uenosa and Solorina saccata. This mode of propaga- tion corresponds exactly with that by which crustaceous lichens with a mycelium of radiating, centrifugal growth, form numerous small balls of gonidia, which by their abundance fuse into a granu- lose thallus; or with that by which Cladonia forms its centrifugally- growing scales (primary thallus) or Stereocanlon its scales which afterwards develop into podetia (Danske Likeners 0kologi, fig. 91); it is no doubt the most natural explanation of the fact, that the form of many foliaceous lichens is that the thallus consists of one or more lobes, which have a base on the surface of the earth itself, and grow 7 from thence unilaterally forward away from that base. The Erect foliaceous lichens are, although erect, very com- monly dorsiventral. So far as my investigations go, they die away below (the spot corresponding with the centre of the procumbent lichens) and keep on growing at the apex. They escape being blow r n away by being fastened by their "haptera" each to the other or to other things (Sernander, 1901). These haptera, which have not been investigated more closely, have been found by Sernander in Ce- traria islandica, cucnllata, hiascens and nivalis, and are transformed cilia, which, as is well-known, are extremely common in this genus. The means of propagation in the foliaceous earth lichens appear to be ascospores, or perhaps pycnoconidia. On the other hand, soredia and detached portions of thallus do not appear to play any part in the dispersal of these species either. Otherwise, the whole class has been as yet very little investigated. It is evident that pro- cumbent foliaceous lichens are w r eak competitors, and are easily covered by other plants. As regards abundance of individuals they also play but a slight role in nature. They have far better chances on stones and trees, and are very common in such stations. The erect foliaceous lichens have far greater advantages in competition, and are much richer in individuals than are the others. Iceland has the following foliaceous earth lichens : The Botany of Iceland. Vol II. 10 146 OLAF GALL0E Cetraria cucullata Bell. hiascens (Fr.) Th. Fr. nivalis (L.) Ach. Dermatocarpon cinereum Pers. hepalicum Ach. rufescens Ach. Leplogium lacerum Ach. scotinuin Ach. Nephroma arcticum L. expallidum Nyl. tomentosum (Hofl'm.) Nyl. Pannaria microphylla Nyl. Parraelia lanata Wallr. Peltigera aphtosa L. canina (L.) Fr. horizontalis L. lepidophora Nyl. malacea (Ach.) Fr. polydactyla(Neck.)Hotlm. rufescens Fr. venosa (L.) Hoffm. Physcia pulverulenta Nyl. (v. muscigena). Solorina bispora Nyl. crocea Ach. saccata L. The Fruticose earth-lichens. Three types may be distin- guished, which are however connected by intermediate forms, namely, Hypothallus-wanderers, Podetium-wanderers and Primary-scale-wanderers, which have been exhaustively des- cribed and for the first time established by me in 1913. From these groups I quote as examples: H y p o t h a 1 1 u s - w a n d e r e r s : Stereocaulon condensatum, Cladonia papillaria, C. pyxidata, C. pityrea, C. fimbriata, C. squamosa, C. cris- pata, C. cornuta, C. macilenta, C. Floerkeana, C. coccifera, C. deformis, C. verticillata (see ligs. in Forb. Unders., 1913). Podetium-wanderers: Stereocaulon tomentosnm, S. evolutum, S. coralloides, S. paschale, Dufourea arctica, I), muricata, Siphnla cera- tites, Cladonia degenerans, C. gradlis, C. furcata, C. rangiformis, C. 11/1- cialis, C. rangiferina , Thamnolia vennicularis , Alectoria ochrolenca, Cornicularia aculeata, Bryopogon jnbatns v. nitidnhis, Sphcerophorus fragilis (see figs, in Forb. Unders., 1913). Primary-scale-wanderers: Cladonia foliacea (see figs, in Forb. Unders., 1913). As an example of the structure of a hypothallus-wanderer, a description of Cladonia pyxidata will suffice. When the spore in this species germinates, it gives rise to a mycelium which spreads out radially in the ground (Dan. Lik. 0k., fig. 39 a), and is called a hypothallus. Wherever these purely mycelial hyphse encounter Pleiiro- coccus-algse on the surface of the ground, they establish as has already been described by Krabbe (1891) and Wainio (1898), - a connection with these latter, and form lichens. We may then, on a somewhat older hypothallus, distinguish between the purely my- celial hyphae, which have not as yet begun their lichen-formation, and within these (nearer to the germinating point) a belt, where the I.K.HKNOLOGY OF ICELAND 147 primary scales are fully formed, and in the centre, still older scales with podetia, which are frequently placed distinctly in a circle ("fairy ring"). The hypothallus can wander in the ground for years, exactly as a fungal mycelium wanders; the podetia, on the other hand, live a few years only, and are gradually replaced by new ones. They are erect as long as they are alive, and end by dying away at the base, so that, ultimately, they rot and fall down, as they very rarely cohere with one another by haptera. This type is the most primitive of the fruticose lichens, as is shown by the fact that it is still the vegetative thallus which keeps on living, while the podetia, the curiously transformed apothecia- stalks, die away and are destitute of all the peculiar contrivances which are found in the type of podetium-wanderers, such as pro- strate, creeping podetia, haptera, etc. It is, however, a type which is well-adapted to live on the ground, which the hypothallus can easily penetrate. On the other hand they are ill-adapted for life on the bark of trees or on stones, which can only with great difficulty be penetrated by the hypo- thallus. Nor do there occur, as far as is known, any species among the bark or rock lichens which may be included among the hypo- thallus-wanderers. On the other hand, they are more unfavourably situated in regard to competition than are the podetium-wanderers, which die away below and keep on growing at the apex, by which means they can outgrow several other species. They are also far rarer as regards individuals than are the excellently equipped po- detium-wanderers, Alectoria ochroleuca, or Cladonia rangiferina. Cladonia rangiferina is the most highly developed of all the podetium-wanderers we know. When the spore germinates, a crust-shaped thallus is formed, but this is very rarely obtained, and has been observed only by a few lichenologists, (Krabbe, Wainio and Gallee), as it is very small and disappears very quickly. Upon it the first podetia are developed, and they branch rapidly. The primary thallus dies away and from henceforward the podetium is left to look after itself; it gradually dies away at the base, but keeps on growing "per secula" (Wainio) at the apex, so that it gradually comes to rest upon a cake of lichen-peat made by itself. By the dying aw r ay of the podetium, its lateral branches become gradually isolated from one another; those that are placed somewhat hori- zontally come gradually into touch with the surface of the ground, and take hold of it at their apices by sending pencil-shaped haptera 148 OLAF GALL0E into it(Ment/, 1900; Sernander, 1901 ; Galloe, 1908 and 1913). The podetium-branch thus anchored forms new vertical branches, which in turn also die away below, etc. All the vertical podetium -branches and podetia, which are naturally very slightly attached to the ground (by the decaying bases), are mutually connected by numerous hap- tera, which hold them so closely together, that it is impossible to obtain uninjured any isolated podetium from a tuft. The characteristic features of this type are, that the primary thallus (here crustaceous) very soon dies, and that the podetia (at the edge of the tuft) may lie down horizontally and wander in this way, attached to the ground and to one another by haptera, while they die away at the base, and keep on living perhaps for centuries at their apex. The podetium-wanderer is an excellent earth-lichen-type, cap- able of competition beyond any of the others, by the fact of its dying away at the base, and keeping on growing at the apex, which enables it to grow above both crustaceous and foliaceous lichens, and also above hypothallus- and primary-scale-wanderers. The type is consequently exceedingly rich in individuals in nature; reindeer moss, as is well-known, is the most abundant earth-lichen in the world. But the type is poor in species. It is not adapted to life on rocks and trees, for its dying away at the base would deprive it of its substratum. The primary-scale wanderers are represented by Cladonia foliacea, which is in reality intermediate between a fruticose and a foliaceous lichen. The spore, on germinating, quickly forms a pri- mary thallus consisting of large, well developed lobes, which spread out in a tuft-formation over the ground, while the hypothallus de- cays quickly. Along the edge of the tuft the lobes lie horizontally, but towards the centre they stand upright. They die away at the base, and keep on growing at the apex, exactly as in Cetraria, for instance. They are closely connected with one another by numerous haptera, which prevent them from being scattered to the winds. Consequently, so far, C. foliacea is a foliaceous lichen, but podetia may also be developed on the lobes of the thallus although not frequently in Denmark or in Iceland - - which makes it impossible to include it, as a matter of course, among the foliaceous lichens. The primary-scale wanderers, as regards their competitive capacity, are like the lower species of the erect foliaceous lichens; they are few in number both as regards individuals and species. The fact LICHENOLOGY OF ICELAND 149 that they die away at their base make them unfit for life on the bark of trees and on stones, and consequently they do not occur there. Some fuller data concerning the biology of the fruticose lichens will be given here : The hypothallus is the purely mycelial lichen-tissue, free of gonidia, which is formed by the germination of the spore (the so- redium or perhaps the pycnoconidium). It has been observed in all the species of the genus Cladonia, and in Stereocanlon conden- satnm; but as to all the other species of the latter genus it has, in some, never been observed, and in others, is very insignificant, and is then, only for a time, of importance to the life of the species, as it dies away early. It lives long in all hypothallus-wanderers, and constitutes - as suggested by the name their only means of wandering. On the other hand, it disappears very early in the primary-scale wanderers, and in the majority of the podetium- wanderers. It is always formed of very loosely woven hyphae, which grow centrifugally from the germination -centre. Wherever green algae suitable for the species, is encountered by it on the surface of the ground, it weaves its hyphae round them, and forms thereby the first beginning either of primary scales (Cladonia) or of direct po- detia (Stereocanlon). This process has, as regards Cladonia, been described by Krabbe (1891) and Wainio (1898). Some of the hypothallal hyphae are often formed as fairly thick, dark hyphal bundles, almost devoid of intercellular spaces, especi- ally where they are continued up into the base of the primary scale (Cladonia cornnta, C. uerticillata). The hyphae easily come into con- tact with mineral-grains, humus-particles, plant-remains with their structure still intact, and earth algse. About this the following is to be noted: Mineral-grains, especially sand-grains, adhere to the hyphae of several species. I believe that this happens through the cell-walls being covered with a slight (microscopically-invisible) covering of mucus. The sand-grains themselves are always finely striated on the surface, no doubt from weathering, for it cannot be proved that the hyphae exercise any chemical influence upon them, and we must be careful not to state definitely that the roughnesses are marks of corrosion. The humus-particles are opaque under the microscope. Where 150 OLAF GAI.I.0K they are lying interwoven with the hyphae-bundles, it cannot be shown that the hyphoe affect them. I have observed them very commonly in Cladonia pityrea, sauamosa, crispata and Floerkeana. Plant-remains, with their structure intact, occur very commonly in the hypothallus. Thus I have found Cladonia pityrea adhering to the bark of a dead heather-twig. The hyphae of the hypothallus behave here exactly as does the hypophloedal hyphal system in the bark-lichens: The cork-lamellse were split from one another into small-scales, but the cork could not be proved to have been cor- roded by the hyphae. The same lichen often spreads out its hypo- thallus over dead moss-leaves on the ground, but these have, as a rule, turned so brown and are so broken, that it cannot be shown whether the hyphae have had any part in their disintegration. Very commonly the hyphae encounter various green algae and Cyanophycece (Gloeocapsa, etc.); in no case did I find haustoria in the algae, nor did I, on the whole, see the hyphae attach themselves to the algae, or by their mode of branching, etc. show the least interest in the algae in question. They appear almost always to be of no importance whatever to the lichen-hyphae, even if they are lying encysted amongst them. The fact that dead specimens may be found amongst them does not show with any certainty that death is due to any influence exerted by the lichens, although the pos- sibility of it is not excluded. The primary thallus (in Cladonia} consists, as is well-known, of small, leaf-shaped thallus -scales of dorsiventral structure, which proceed directly from the hypothallus, and are developed in centri- fugal succession from it. In all hypothallus-wanderers the primary scales live very long as "nutrition-shoots," co-equal with the podetia. They are of far less importance to the more primitive podetium- wanderers (Cladonia gracilis, fnrcata , ranyiferina) in which the podetia, at an early stage in the plant's life, become its chief, and finally its only assimilatory organ; finally, in the more advanced podetium-wanderers (Cladonia rangiferina, nncialis), they are so in- significant, that they form quite a crust-shaped thallus, which perishes so early, that the majority of the lichenologists have not even seen it. Moreover, several podetium-wanderers are, as a rule, propagated in quite a different manner (by fragments of podetia, etc.) and thus have, on the whole, very rarely any opportunity of developing a primary thallus. LICHENOLOGY OF ICELAND 151 In Cladonia foliacea the primary thallus is the chief assimilatory organ of any length of duration. Consequently, three types may be distinguished: (1) Permanent primary thallus, which keeps on growing along the edge and dies away at the base; this is found in the primary-scale- wanderers (Cladonia foliacea). (2) Permanent primary thallus, which does not die away behind, found in the hypothallus-wanderers and in the more primitive podetium-wanderers (Cladonia papillaria, pyxidata, pityrea, fimbriata, squamosa, crispata, cornnta, macilenta, Floerkeana, coccifera, deformis, verticillata,gracilis, rangiferina, furcata). (3) Quickly perishing, crust-shaped primary thallus, found in the most decided podetium-wanderers (Cladonia uncialis and rangiferina). From the under surface of the primary scales, in several cases, hyphae may proceed from the cortical layer. Sometimes it is difficult to decide with any certainty, whether they are simply hypothallal hypha? or which may be the case secondary hyphae, which from the medullary layer, push their way into the soil, and attach themselves to it, and are therefore, properly speaking, haptera. Un- doubted haptera I have found in Cladonia foliacea, where they occur in the form of a hyphal pencil, in C. pityrea, where they are similar in form, in C. squamosa, where they form solid hyphal bundles, and in C. pyxidata, macilenta and furcata, in which they consist of scat- tered hyphae, produced from the under surface of the scales. The haptera attach themselves to mineral-grains, humus-lumps, etc., in exactly the same manner as do the hypothallal hyphae, and it is true also with regard to them, that it has not been possible to demonstrate microscopically that they have any chemical influence. Interwoven in a hapteron of Cladonia foliacea I found green algae, which \vere apparently uninfluenced by the proximity of the hyphae. Another type of primary-scale haptera I found in Cladonia foli- acea and in C. cornnta. By means of these the scales attached them- selves to one another or to podetia of the same species. Podetia. Of these, four types may be distinguished, which differ in duration of life and in mode of growth. All the fruticose earth-lichens are erect, and their thalli are, as a rule, called "podetia," but these, however, differ greatly in the history of their development. Here the term is used as a biological conception to indicate the subaerial thallus, mainly of a radiating form ; (consequently not the primary scales of Cladonia). Of this I have set up four types, viz. (1) erect, radial, permanent podetia; (2) erect, radial podetia, dying 152 01. AF GALL0K away at the base; (3) procumbent, dorsi ventral, hapteron-producing podetia, dying away at the base behind; (4) procumbent, dorsiventral, hapteron-free podetia, dying away at the base behind. Type 1 is found only in the hypothallus-wanderers, and in the majority of these. Type 2 is found in some of the hypothallus-wanderers, and in all the podetium-wanderers. As a rule, we may take for granted that podetia of type 1, when they become old, ultimately pass over to type 2 for a short time, before they die away entirely. But even if the boundary line between the two types is thereby made very uncertain, it is advisable to maintain both of them, as there are undoubtedly species which never die away below or, at any rate, very rarely do so (e. g. Stereocaulon condensatnm, Cladonia papillaria, (]. pyxidata, C. pityrea and possibly others). Type 3 like type 4 is commonest in the podetium-wanderers, in which the edge of the tuft usually grows in circumference by the marginal podetia lying down and creeping over the surface of the ground, and like runners spreading out on the substratum. By this the podetia often become somewhat dorsiventral and, in addi- tion, send in some cases haptera into the ground (the majority of the podetium-wandering Cladonias); in other cases nothing like this happens (Stereocaulon, Dufourea). Consequently, in the same tuft and in the same species more than one type of podetium may be found, so that types 1 and 2 are united, in that the old podetia may belong to type 2, and the young, on the other hand, to type 1 ; but, as already mentioned, in some species type 1 is the dominant one. Types 2 and 3 are, as a rule, united in the same species and in the same tuft, in that type 3 forms the runners of the tuft, and type 2 the old erect shoots in the middle of the tuft. In the same way, types 2 and 4 are as a rule united in the same tuft. It is evident, that all species which have on the whole erect, permanent podetia, are less adapted to grow on the earth, because they are so dependent on the substratum for their attachment, and are therefore easily overgrown and crowded out by other species. Their apical growth also is very limited, which in addition reduces their capacity for competition. Podelium-wanderers, on the other hand, are excellent compe- titors. With regard to these I shall add some further notes about LICHENOLOGY OF ICELAND 153 the relation of the podetia to the substratum and mutually to one another. As already mentioned, the oldest podetia die away below, and form thereby a peaty mass, while they keep on growing at their apex "per secula" as Wainio writes. The question now arises how the podetia, on a century-old cake of lichen-peat, obtain their mineral food. So long as the lichens are in somewhat close contact with mineral soil, every shower will saturate the upper layers of earth, and the water will become nu- tritive to a certain extent. But later on, when the cakes of lichen- peat are formed, they will no doubt gradually become washed free from minerals, and the -water which the lichens can absorb from the substratum (which is, as is well-known, very little, because they lead the rainwater down into the ground much more easily than upwards from it, as demonstrated by Zukal, 1891 96) must be- come poorer and poorer in nutriment. Can this ultimately bring about the result that the lichen-covering, by its continued growth, brings about its own destruction? It is a question which lichen- ologists, who have easy access to Alpine lichen-heaths, ought to take up for investigation. Haptera have been first demonstrated and described by Ser- nander (1901) in a small and very interesting, but unfortunately only too brief, treatise. Sernander distinguishes several types (Cladohia-type, Alectoria-type, etc.). I prefer another classification, because haptera of several different types occur on the same plant, and cannot therefore be named after different genera. Sernander does not describe them anatomically. In my "Forberedende Under- sogelser" (1913) they have been very fully treated and figured, and the chief points will now be recapitulated here. According to my classification the types to which the haptera may be referred, are the following: (1) Apical haptera, (2) Lateral haptera, (3) Primary-scale haptera, (4) Podetium-scale haptera. Some of these, especially the two last, have not been mentioned at all by Sernander. The haptera may attach themselves to the ground (when the podetia are procumbent); or to other individuals of the same species (but no parasitic relation ever arises from this contact) ; or to other 154 OLAF GALL0E species of lichens (again no parasitic relation appears to arise), or, lastly, to quite other plants, e. g. moss, heather, etc. Apical haptera put into the ground I have found in the more differentiated podetium-wanderers, with distinctly procumbent mar- ginal podetia, the apices of which occasionally come into contact with the ground, and are then immediately transformed into pencil- shaped bundles of hyphae, which penetrate into the ground, and fix the podetia for the time being, and absorb water and nourish- ment. The hyphae are frequently H- shaped by attachment to one another (fusions), and they behave exactly like hypolhallal hyphae; they attach themselves to mineral-grains, humus-particles, and dead plant-remains with the structure intact, nor can it be microscopically proved that they affect these bodies chemically. In one single case 1 have seen earth-algae (Zygogonmm-f\\amenis) entangled and attacked by the haustoria of the hyphae, namely in Cladonia rangiferina; otherwise earth-algae do not appear to be attacked by them. Apical haptera put into the ground I have found in Cladonia furcata. Apical haptera which attach themselves to individuals of the same species, I have observed in Cladonia crispata, coccifera, rangi- formis, rangiferina, Cornicularia acnleata. Apical haptera which attach themselves to the podetia of other species, I have found in Cladonia degenerans, rangiformis, uncialis, rangiferina, Alectoria ochroleuca, Cornicularia acnleala, Bryopogon jubalus v. nilidiilus. In none of these cases does the part attacked appear to sustain any damage. The haptera appear to be exclusively organs of attachment, not suckers. The lateral haptera put into the ground (in Cladonia gracilis, furcata, rangiformis, uncialis, rangiferina) are biologically identical with the apical haptera put into the ground. Lateral haptera between podetia of the same species (in Cladonia papillaria, crispata, coccifera, Dufonrea arctica. mnricata, Cladonia gracilis, rangiformis, uncialis, rangiferina, Thamnolia vennicularis, Cornicularia aculeata, Si>ha>rophorus fragilis] are widely distributed. The cortical layer of the podetia grow mutually together, but the gonidium- and the medullary layers are not at all influenced by this. A totally different kind of haptera is found in Siphula ceratites, where the podelia grow completely together, cortex with cortex, medulla with medulla, etc.; Sernander has described this (1901). Lateral haptera put into other species (heather, moss and other lichens) I have seen in Dufourea arctica, Siphula ceratites, Cladonia r.ICHKNOLOGY OF ICELAND 155 degenerans, uncialis, Thamnolia vermicular is, Cornicularia acnleata, Bryopogon jnbatns v. nitidulns, Sphcerophorns fragilis\ they play ex- actly the same role as do apical haptera put into other species. Primary-scale haptera I found only in Cladonia foliacea. By means of them the primary scales of long duration which die away at the base, are attached to one another; no parasitic relation arises by this attachment. Podetium-scale haptera I found only in Cladonia cornuta. By means of them the podetia are attached to one another, the scales of the one podetium attaching themselves to the wall of another podetium of the same species; no parasitic relation arises by this attachment. When procumbent podetia are buried in the ground, they die. No species known to me can endure being covered with earth for a long time. First the gonidia appear to die, sometimes after a short period of intense division, which is probably occasioned by the increased dampness. Then the lichen-hyphre die, the walls, as a rule, turning brown. The fruticose earth-lichens are propagated in a widely different manner according to their morphological structure. Hypothallus- wanderers very commonly bear fruit, and are propagated, no doubt as a rule, by ascospores. Some of them are propagated far more frequently by soredia, and in that case apothecia are much rarer in them (Cladonia fimbriata, deformis), so that in such species there appears to exist a correlation between these two modes of propa- gation. In others again these two modes of propagation appear to be equally common, a quantity of soredia and apothecia being de- veloped on the same individual. However it requires to be more closely investigated, whether the asci in strongly soredia -bearing individuals are empty, as they frequently are in Cladonia. In the podetium-w^anderers propagation takes place in several cases by the breaking off of fragments of podetia which are then carried away by the wind to other places where they form new tufts. This has already been described by Wainio (1808) and after- wards mentioned by Mentz (1900) and Galloe (1913 and 1918). Species of Stereocaulon do not appear to be able to propagate themselves in this way, as podetia-fragments have not yet been observed to put out haptera into the ground. On the other hand, they are often found bearing apothecia. Of fruticose earth-lichens Iceland has the following: 156 OLAF GALL0K Alectoria divergens Ach. Cladonia pityrca. jubala L. pyxidata. nigricans Nyl. rangiferina. ochroleuca Nyl. rangiformis. Cetraria aculeata Fr. turgida. Cladonia amaurocrsea. uncialis. bellidiflora. verticillata. cariosa. (Polychidium muscicolaSw.,dwarl- coccifera. formed). decorticata. Sphserophorus fragilis L. fimbriata. Stereocaulon condensatum Hoil'm. Floerkeana. incrustatum Flk. foliacea. paschale (L.) Fr. f'urcata. tomcntosum(Fr.)Th. Fr. gracilis. Thamnolia vermicularis Schaer. These and numerous other species have been specially treated in "Forberedende Undersogelser" (1013), to which the reader is referred. 4. ROCK LICHENS. When the climatic conditions are favourable to the growth of lichens, a lichen-vegetation may eventually develop on a rocky sub- stratum. But other demands also must be satisfied, namely those which have regard to the physical and chemical conditions of the substratum. Many different rocky substrata may be distinguished, and some differences in their lichen-vegetation may also be pointed out. The most important physical conditions are, as far as is known, the following: Stahlecker has observed that on stratified rocks lichens first choose those surfaces which are perpendicular to the stratification. How this phenomenon is to be explained is yet unknown but, a jtriori, we might be tempted to believe, that the lichen-hypha? more easily penetrate the rock parallel with the stratification, than trans- verse to it (compare with this the fact that wood-lichens are best able to grow parallel with the "fibres" of the wood). Perhaps such surfaces disintegrate also more quickly. The importance of the chemical conditions are far better known, owing to investigators like Krempelhuber, Fu is ting, Stein er, Zukal, Zahlbruckner, Hulth, Bachmann, Funfstuck, Lang, Friederich and Stahlecker. The researches of these investigators have proved that there is a distinct anatomical difference between lichens from primitive rocks, LICHKNOLOGY OF ICELAND 157 (silica-lichens), and those from calcareous rocks, (calcareous lichens), although the observers disagree somewhat among themselves as regards the explanation of this phenomenon. Stahlecker has shown that rocks composed of different kinds of mineral-grains, are affected by the lichens so that the basic grains are the iirst to be corroded, then the acid. The physical and mine- ralogical qualities of the mineral-grains are, on the other hand, of no importance. The same author maintains that lichens are able to corrode quartz; this is denied by Bach ma nn. On the other hand, how rocks with glassy structure, without distinct, separate grains of mineral matter, as for instance obsidian, the ground-mass in porphyries, pumice, etc., are affected, is not known. The corrosion must be assumed to take place in part actively on the part of the hypha3, by their excreting acids. But nothing is known regarding this point. The degree to which the rock is disintegrated is, as I have shown (1908, p. 300), of great importance, the freshest, recently-bared rock-surfaces being devoid of lichens, while progressive disintegration is accompanied by the presence of crustaceous, foliaceous and fruti- cose lichens in fixed succession. As far as my knowledge and that of other investigators goes, I must assume that a floristic difference will be proved to exist in the lichen-vegetation found on different kinds of rock, especially between that found on calcareous and siliceous rocks a circum- stance which is already partially known. It is thus seen that both floristically and biologically the che- mical condition of the substratum is the determining factor, whilst its physical condition appears to be less important (compare above on bark-lichens). But as yet exhaustive lists of lichens from different kinds of rock are wanting, and these alone can give a closer in- sight into this floristic difference. That species exist which are con- fined to one particular substratum, for instance lichens which are exclusively "calcareous lichens," is quite certain, but I do not think it has been definitely proved. Rock-lichens may be divided into three groups: cruslaceous, foliaceous and fructicose lichens. In the crustaceous lichens two sub-groups may be recognized: the epilithic and the endolithic. The epilithic crustaceous lichens have a hyphal layer 158 01. AF (, V1.I.0K devoid of gonidia, which is sunk into the substratum and which corrodes the individual grains of mineral matter. According to A. Friederich this hyphal layer is thin in the silicicolous lichens, and cannot at all be compared, as regards size, with the corres- ponding tissue in the calcareous lichens. Besides, according to Friederich, it is never furnished with oil-hyphse or sphaeroid- hyphse; but according to Bachmann, such are said to occur. At any rate, Fiinfst tick's investigations show that where the same lichen grows both on calcareous and on siliceous rocks, the indi- viduals from the calcareous rocks contain oil, while those from the siliceous rocks do not. Ftinfsttick, whose results have since been strongly supported by E. Lang's renewed investigations, appears to differ somewhat from Bachmann as regards the occurrence of oil-hyphse in the silicicolous lichens; this disagreement need not, however, be a fundamental one, as there will probably be various degrees with regard to the oil-contents connected with the larger or smaller amount of lime contained in the rock-species in question. At any rate, it is certainly an undisputable fact that the amount of oil is greatest in the calcareous lichens. The biological importance of the oil-contents is much contested. Zukal is of opinion but quite wrongly, according to Ftinf- st tick's investigations, - that the oil is a supply stored for fruit- setting. Hulth also, regards the oil-containing tissue as reservoirs for reserve food-material. Funfstuck shows that there exists no connection between the fruit-setting and the oil-contents, and is of opinion, that the oil is an excretion formed owing to the accumula- tion of the carbon dioxide, which is set free by the hyphse pene- trating into the calcium carbonate. As mentioned by Bachmann and Stall lecker the hyphae affect the mineral grains in various ways. According to Stah lecker they corrode quart/. This is denied by Bachmann. Basic mineral- grains are affected before the acid mineral-grains, according to Stall 1- ecker. When there is a decided cleavage-plane in the mineral-grains (as in mica), the hyphae, according to Bachmann, follow the di- rection of the cleavage, whereby the existing cleavages are widened and filled with hyphae. The epilithic part of the thallus contains gonidia. It frequently consists of a growing lichen-mycelium produced centrifugally from the centre of germination, bearing on the thallus numerous small, rounded or irregularly angular areas containing gonidia; according LK.HENOLOGY OF ICELAND 159 to Friederich, these gonidia-areas have come into existence in places where the gonidia (algae) have accidentally fallen on the lichen-mycelium. According to Stall lecker each area has originally been an independent thallus, which, by coming into contact with similar neighbouring thalli, forms with these a "Gesamtthallus," which may afterwards grow as a unity, starting from a common centre. This interpretation sounds quite incredible, and I think it is very rarely, if ever, in accordance with fact. Can it, on the whole, be understood that these smaller thalli are "independent," as they have all been produced by the same lichen-mycelium? It is quite another question, whether a group of really indepen- dent thalli, produced each from its own ascospore, on meeting, can alter and carry on a joint growth. About this nothing is known, a priori, it does not seem very probable. In reality, these small thallus-patches containing gonidia, men- tioned by Stah lecker, must quite naturally be regarded as ana- logous, for instance, to the primary scales in Cladonia, which are also small green gonidia-containing thalli on a common mycelium; or with the exactly corresponding balls of gonidia in numerous crustaceous earth-lichens (Lecidea alpestris, L. uliginosns, etc.). Quite another separation into patches may moreover take place by existing patches splitting asunder into separate parts by growth- tensions (or by drying?) (see "Dan. Lik. 0k.," fig. 19, a, b, c, d). When the thallus is smooth and non-partitioned, Stahlecker is of opinion that it is an old, formerly partitioned thallus. I can- not believe this interpretation of the condition. Friederich has found the gonidia-layer of the silicicolous lichens to be thicker than that of the calcareous lichens, Funf- stiick has also found this to be the case. The mode of propagation has been investigated by Bee km an n, who found that some species (Lecanora badia, L. cenisea), the thalli of which are partitioned, ma} 7 reproduce by means of detached portions of the thallus, whereas soredia are absent. On the other hand, the partitioned thalli of the Rhizocarpon spp. do not appear to be able to reproduce in this way. Thin, cohering (non-partitioned) thalli do not appear to be able to reproduce in this way. Whether this mode of propagation, on the whole, plays any important part in nature, compared with pro- pagation by spores, I regard as doubtful. With regard to capacity for competition, the crustaceous lichens 160 OLA1 GALL01 have no equals when the surface of the substratum is fresh, i. e. has been recently bared or is non-disintegrated. They cannot, how- ever, live on very recently bared rock; a slight inorganic disinte- gration must first take place, and then they make their appearance. They themselves contribute towards disintegration whereby they prepare the substratum for other, more pretentious forms (foliaceous and fruticose lichens) and so bring about their own destruction, as mentioned in "Dan. Lik. 0k.," p. 360. The endolithic crustaceous lichens appear to occur only on calcareous rocks. As an example may be mentioned Biatora immersa (Web.) Arn., which is exhaustively treated by Funf stuck. There is in this species a slightly developed epilithic thallus, con- taining gonidia, which at the base passes over into a more vigorous endolithic thallus, with a great abundance of oil-cells of various forms. There is evidently a certain connection between the great abundance of oil in the thallus, and the chemical nature of the substratum, especially its wealth of carbonates. This class and the calcareous lichens richer in gonidia, that is to say, on the whole, the endolithic and the epilithic species, are connected by a series of intermediate forms; and there is hardly any lichen which is endolilhic in the sense that the whole of the thallus is hidden in the substratum and covered over by it. For the rest, there are many points in the natural history of the endolithic lichens, which still remain to be explained. With regard to special modes of pro- pagation, nothing is known. At the point of transition between crustaceous and foliaceous lichens there stands a group of "placoid" species (Beck man n, 1 ( .H)7), for instance, Placodium (Lecanora) sa.ricola, Caloplaca mnrornm. Dimehcna ore'ina, all of which have along their edges leaf-like thallus-lobes, devoid of cortex on their under surface. In Placodinm saxicola there may occasionally be found an indication of a cortical layer on the under surface, when it is growing on a smooth, polished rock-surface (Dan. Lik. 0k., fig. 62, b). Beck- in an n has shown that the species mentioned here may be propa- gated by the thallus-lobes becoming detached, and sprouting out into new individuals. Of crustaceous lichens Iceland has the following species: Acarospora discreta. Arthoniu ruderalis. fuscata. Bacidia caudata. Heppii. coprodes. LICHENOLOGY OF ICELAND 161 Bacidia milliaria. sphieroides. subfuscula. Bseomyces byssoides. Biatorella Morio. Buellia sethalea. atroalba. badia. coniops. leptocline. mj r riocarpa. stellulata. tesserata. vilis. Caloplaca aurantiaca. cerina. citrina. diphyes. elegans. ferruginea. murorum. pyracea. vitellina. Catillaria athallina. lenticularis. Diploschistes scruposa. Gyalecta cupularis. Haamatomma coccineum. ventosum. Lecania athroocarpa. Lecanora albescens. alphoplaca. alpina. atra. atriseda. atrosulphurea. badia. calcarea. cartilaginea. chrysoleuca. cinerea. cinereorufescens. coarctata. frustulosa. gelida. gibbosa. Hageni. lacustris. pallescens. poliophasa. Lecanora polytropa. saxicola. sordida. straminea. subi'usca. tartarea. varia. Lecida aglasa. arctogena. atrobrunnea. atrorufa. auriculata. cinereoatra. confluens. contigua. convexa. crustulata. cyanea. Dicksonii. elata. elseochroma. erratica. fuscoatra. furvella. impavida. lapicida. lithophila. lugubris. panasola. pantherina. paupercula. Siebenhaariana. speirea. subconfluens. tenebrosa. vernalis. Lepraria. Pannaria elceina. granatina. Hookeri. microphylla. Pertusaria corallina. rhodoleuca. Placynthium nigrum. Polyblastia Henscheliana. hyperborea. Rhizocarpon alboatruin. calcareum. geminatum. geographicum. The Botany of Iceland. Vol. II. 11 1()2 OLAF GALL0K Rhizocarpon petraeuiu. Verrucaria niargacea. viridiatrum. mucosa. Staurothele clopima. nijrescens. Verrucaria maura. rupestris. As regards a few of these species it is true that they not only occur on common rocks, hut also on disintegrated, bleached bones of various animals, usually on bones of sheep, which are ratlin commonly found lying out in the open air. With regard to this point further particulars will be found in the table of the chief biological conditions of the different species. The Foliaceous rock-lichens. The numerous species of Umbilicarid. (iijrophora, Parmelia. etc., may be sub-divided into at least two types, viz. the Gyrophora-iype and the Parmelia-(\[>e. The Gj/ro/;/io/'-type (Gyrophora, Umbilicaria), as we know, con- sists of lichens which are attached to the substratum at a single point on the under surface of the thallus the "umbilicus''. This is the reason why the lichens cannot die away in the centre and form "fairy rings." With regard to absorbtion of food from the sub- stratum, such species are differently conditioned from the Parmelia- like-lichens which are attached to the substratum at various points. With regard to capacity for competition, all the species stand very high, as they very easily grow across their competitors. Hence, in many places in Arctic regions, they form, on the rocks, growths very conspicuous and rich in individuals. The Parnielia-i\pe. Its many species are attached to the sub- stratum by numerous rhizines, and die away in the centre, forming "fairy rings, " without thereby losing their foothold. This feature is very commonly seen in Parmelia saxatilis. The ordinary anatomical structure has already been long known from the investigations of Sc h wen dene r and others. 1 shall only draw attention to the fact that there are cortical layers on both sides, as also a gonidial and a medullary layer. The morphological structure still requires much investigation, especially from a biological point of view. The means of propagation are, in addition to ascospores, in some species soredia also. How widely distributed the latter are, is not known. Propagation by means of detached portions of thallus, does not appear to have been observed in any of the species. In competition the foliaceous lichens are far superior to the crustaceous lichens, when the substratum has, in some measure, LICHENOLOGY OF ICELAND 1(53 been prepared by the growth of the latter. I have never observed any foliaceous lichens on a quite recently bared surface. The crusta- ceous lichens appear always to be the first to arrive, and are after- wards succeeded and exterminated by the foliaceous lichens. Of Foliaceous rock-lichens Iceland has the following: Cetraria Fahlunensis. Leptogium plicatile. Collema crispum. Parmelia alpicola. flaccidum. encausta. pulposum. incurva. Dermatocarpon miniatum. lanata. Evernia furfuracea. olivacea. Gyrophora arctica. physodcs. cylindrica. saxatilis. erosa. stj'gia. hyperborea. Physcia aipolia. murina. aquila. polyphylla. caesia. proboscidea. Xanthoria lychnea. vellea. parietina. The Fruticose lichens are not numerous. As I have previously shown, they rest almost exclusively on a substratum prepared by other lichens, and consequently are not really true rock-lichens, as they are dependent on the peat-formation, which the first inhabitants of the rocks leave behind them on their decay. Consequently, if we investigate more closely such apparently rock-inhabiting species of Stereocaulon and others, we shall find under them not rock but first a thin layer of peat, and under that, the rock. Consequently, they are in reality earth-lichens. A few species are, however, undoubtedly true inhabitants of rocks, for instance Usnea melaxaniha, Roccella, Ramalina and a few Stereocaulon spp. They have at their base a permanent thallus, which is thread-shaped (Usnea) or ribbon-shaped (Ramalina) and isolateral. Formation of haptera between the individuals (see under earth-lichens) is unknown, and would appear also to be rather superfluous, as they do not die away at the base. Consequently, as regards these two points, they appear to differ greatly from their fruticose relatives among the earth-lichens, which is quite in harmony with the different substratum. Special modes of propagation - - by detached portions of thallus, etc., are not known. With regard to competitive capability the fruticose lichens ge- nerally stand very high. In Denmark species of Ramalina can form 11* 164 OLAF GALL0E continuous, almost pure growths on rocks (Ramalina-he\\.) on the cliffs of Bornholm. Species of Roccella appear to form similar carpets on the cliffs of the suh-tropical and perhaps tropical regions. Of Fruticose rock-lichens the following are found in Iceland : - Alectoria ochroleuca. Coenogonium ebeneum. Ephebe pubescens. Lichina confinis. Racodium rupestre. Ramalina scopulorum. subfarinacea. Sphaerophorus coralloides (?). fragilis (?). Stereocaulon coralloides i . denudatum. cvolutum. Usnea melaxantha. With regard to these it should be remarked that it is some- what doubtful how far Racodium and Coenogonium should, on the whole, be reckoned among the fruticose lichens : they have a thread- shaped, somewhat procumbent-ascending thallus. Also a query has been placed against several of the other species, to indicate that it is doubtful whether they are true rock-lichens occurring on bare rock because, at any rate when older, they are rarely, in fact very rarely, attached to the rocky substratum. 5. SYNOPSIS OF THE CHIEF BIOLOGICAL CONDITIONS OF THE LICHENS OF ICELAND. Names Bark-lichens CO 2 "> S 'c,~~ a Earth-lichens Rock-lichens Propagation by Thallus Ascospores Soredia Thallus fragments V ^ i i. (U ^ U *s t <^ " 35 Acarospora discrcta i 1 i 4- + - + + + + 4- + 4- + + + 4- + + 4- 4- fuscata Alectoria divergcns jubata nigricans ochroleuca . .... Arthonia proximclla punctiformis ruderalis . Arthopvrenia anale])ta grisea . Hacidia abbrevians . LICHENOLOGY OF ICELAND 165 Names CO oatrum calcareum gcminatum geographicum petronim viridiatrum Rinodina (lonradi mnianea sopbodes -|- turfacea Solorina l)ispora crocea saccata Spbierophorus coralloides fragilis + 4- 4- + + + + LICHENOLOGY OF ICELAND 171 Names risea. kentrospora. Pvrenula micula If we compare the birches of Iceland and Denmark with re- ference to their lichen-vegetation, a characteristic difference will he seen as regards the species. In Denmark Eoernia Prnnaslri. K. fur- I'liracea, (A'lrarid oldiica. Usnea barbata and lidinalind [dsliaiald form the dominant feature of the vegetation. In Iceland they do not ap- pear to he of any importance, or are quite absent. The number of the species is greater in Iceland, yet I cannot depend upon this not bring due to insufficient investigation of the birches of Denmark. How the matter stands as regards "mass-occurrence" and "fre- quency-number" in Iceland and Denmark, I am not prepared to say, because, as I have already mentioned, I myself have not seen lichen-bearing birches in Iceland. 2. THE EARTH-LICHEN ASSOCIATIONS. In the previous pages we have made a survey of the general biology of the earth lichens. Here we shall consider more closely the special Icelandic conditions, viz. the characteristic qualities of the Icelandic soil, and, finally, the lichen vegetation found in the plant-associations. In a preceding part of this work Professor Thoroddsen has given an exhaustive description of the Icelandic soil, and of its geological and agricultural qualities. To this I refer the reader, and it will suffice here merely to point out such features of it as are of importance to the lichen-vegetation. As stated by Thoroddsen, the Icelandic soil consists entirely of a finely divided mass, derived from the fundamental rock of the island, or of the same chemical and minera logical composition as the latter. In other words it is the Basalt, in grains of every possible size, ranging from enormous blocks of rock to particles as fine as dust, which constitutes the soil available to the lichens all over Iceland. The liparite which occurs here and there is, ac- LICHKNOLOGY OF ICELAND 175 cording to Thoroddsen, oi' no importance as far as soil-formation is concerned. Consequently, whether the soil is of the one or the other geo- logical origin - glacial soil, or soil deposited in water, or deposited by wind, (aeolian deposits) its chemical or mineralogical com- position is essentially the same in all cases. The circumstances which are of importance, regarding the soil as a lichen-substratum are therefore essentially the following: (1) The chemical composition (mineral earth or earth rich in humus), (2) the size of the grains, (3) thermal conditions, (4) the water-contents, (5) drifting soil, (6) burrowing ani- mals, (7) leaf- fall, (8) and the snow-covering. To these must be added, what is perhaps the most important, (9) competitive relations with other plants. (1) The chemical composition of the loose soil is, as a whole, somewhat different in Iceland from that in Denmark, as was first pointed out by P. Feilberg (see Thoroddsen, in vol. I, p. 252, of the present work). With regard to the amount of nutri- tion present, the difference is doubtless of very little consequence as regards lichens. On the other hand, it is indirectly a highly im- portant fact, that the great amount of iron-salts and humus cha- racteristic of the soil of Iceland, conditions a plant-growth which, taken as a whole, is very widely different from that of Denmark, and causes a competition among the plant-species which is highly conducive to the wide distribution of lichens all over Iceland. (2) The size of the grains (fineness, respective coarseness) of the soil is, as mentioned above, hardly of any direct importance, but no doubt of indirect importance by being the means of bringing about various conditions of heat and moisture in the finer and coarser kinds of soil. (3) The thermal conditions are far more unfavourable in Iceland than in Denmark, far greater tracts of ground being frozen, during a greater part of the year. As long as the upper soil-layers are frozen, the plant-covering also will frequently be thoroughly chilled, and the lichens will therefore lie dormant. On the other hand, it hardly has a direct influence upon the lichens if the ground is frozen farther down, as they are attached to the ground only very superficially, frequently only a few millimetre at the uppermost part near the surface. Quite another and far greater but indirect role is played by the frozen ground, owing to the fact 176 OLAF GALLOP: that the conditions of moisture are essentially dependent upon it. When the ground thaws in spring, there is a time in which the upper soil -layers are, lor the time being, very wet, because the melting snow and ice cannot sink into the ground, owing to the sub-surface ice. We may be justified in saying that, taken as a whole, the yearly growth-period as compared, for instance, with that in Denmark, is considerably shortened by the low temperature of the soil. How long this period lasts, upon the whole, as regards the lichens, which, as we know, assimilate as soon as the tempera- ture is above free/ing-point, has not been investigated. But I assume that it is far shorter than in Denmark, where it lasts almost all the year round. (4) The water-contents of the soil in Iceland, owing to the great amount of precipitation and the slight evaporation, are far greater than in Denmark. In the surface features of the landscape this is shown by the frequent occurrence of bogs. But, naturally, there is a great difference in the amount of water contained in the various soils, all conditions being found intermediate between boggy soil saturated with water, and dry sandy soil, and soil fine as dust which is so dry in numerous places that it drifts with the wind at every opportunity. The wettest soil, which is continually saturated \\ith water (the bogs), is devoid of lichens; this is also the case with the driest, drifting soil, not on account of its dryness for it is well-known that lichens chiefly imbibe directly -precipitated moisture, and are fairly independent of other water-supplies, - - but on account of the instability of the drifting soil. Lichens grow on soil intermediate, with regard to dampness, between these two ex- tremes ; they grow in association with other plants, as will be fully described below. (5) All drifting soil is devoid of lichens. (6) The role which burrowing animals play in Iceland is not known very particularly; it is however in all probability quite insignificant, while in Denmark, as is well-known, it is very great, especially in the woods. (7) Leaf-fall. The layer of decaying leaves which in Den- mark, during autumn, buries all the small plants of the wood-floor, plays, as a matter of course, a similar role in Iceland. When the trees or the shrubs (willow, birch) stand very close, the ground is frequently devoid of lichens, and this is no doubt partially due to this leaf-covering. LICHENOLOGY OF ICELAND 177 (8) The snow-covering has a very great influence, especially in the mountains. Where there is a perpetual snow-covering, lichens naturally cannot live. But lichens can live even on soil which is free from snow for only a few weeks during the summer. Thus I observed in several places on the mountains around Ofjord that lichens grew abundantly at considerable elevations, which are not freed of snow until July. Taken as a whole it may be said, that the snow-covering in Iceland, by shortening the annual growth- period, plays a far greater role than it does in Denmark. (9) The competitive relations with other plants are, on the whole, more favourable to the lichens in Iceland than in Denmark, because the higher plants - - in consequence of the soil and climate are not generally of so quick a growth there as in Denmark; but this I must naturally discuss more fully under each particular plant-association. For the present I shall only point out that the lichen-vegetation in Iceland plays physiognomically a more dominant role than in Denmark, more particularly because the competition on the part of other plants is not so keen there as it is in the more temperate regions. The combined result of all the factors, climatic and edaphic, which we have been considering above, shows itself in the form of plant-associations as they occur in nature. I shall therefore go through these one by one, and, as far as our present knowledge of the subject makes it possible, occupy myself more closely with what has given them their appearance. With regard to the plant-associations of loose soil, it is difficult to carry out any single logical systematization merely to find proper names for them, such as are characteristic and to the point, is difficult. To do this we can proceed in any one of three essenti- ally different ways: we can (1) name the association after the soil (e. g. "sandy shore," "dunes," etc.), or (2) after the conspicuous, dominant plants found therein (e. g. "beech wood," "birch coppice," etc.), or lastly (3) we may combine these two, as ecologists frequently do, and as people do in common language, naming some associa- tions after the characteristic features of the soil, and others after conspicuous, characteristic plants. In reality it is extremely difficult to decide upon one of these methods in particular, for the following reasons: If there existed The Botany of Iceland. Vol. II. 12 ITS OLAF GALL0E absolute agreement as regards a fixed terminology for the naming of the different kinds of soil, and in addition, if it were possible, out in the Held, immediately to identify to which category the soil belonged which supported the association we were just then in- vestigating, then it would be an excellent method consistently to name the association after the soil. But this cannot be done, owing to the nature of the subject. There does not exist, and will hardly ever be created, any descriptive soil-term, which will win universal acceptance. Nor will it ever be possible, out in the field to identify each kind of soil with any certainty. This requires thorough chemical and physical investigations, which must be made in the laboratory. It appears to be far easier to name the association after the dominant plants, when such occur. A beech wood is easy to recognize as such, but a "fell-field" (rocky-flat) a "mat-herbage" (herb-flat) which are not characterized by any one individual species, how are we to know them? Here we find ourselves in reality placed before a fundamental question in ecology, - the definition and naming of the plant- association: partly, how we shall precisely define the individual association, so that it is recognizable wherever it may be met with on the surface of the earth, and may be determined, at any rate, with as great certainty as we determine a systematic species: and partly, how we shall name it, after the soil, or after dominant species of plant, or perhaps after dominant "growth-forms" (see Warming and Raunkiaer). On this question, first and foremost the founder of ecology, E. Warming, and afterwards C. Raunkiaer, have contended that the associations ought to be analyzed with regard to "growth-forms." so that we may thereby define them. What we shall afterwards call them is a point of less importance, as different names for the same association may be used synonymously, even although a uniform nomenclature would facilitate the survey considerably when we are occupying ourselves with the systemalising of the as- sociations. Which classification of the growth-forms of the plant-world we are to use, must be dependent on the object we have in view in the investigation of the associations. In itself there is nothing to prevent our using several different classifications in the same in- vestigation, for instance, we could enumerate the "geophytes," "hemi- cryptophytes," "chamsephytes," etc. (according to Raunkiser's clas- LICHENOLOGY OF ICELAND 179 sification), or the "summer-annuals," "csespitose plants," "creeping- herbs," "shrubs," etc., etc. (according to Warming's classification). It is in reality a hopeless task to try to describe a plant-asso- ciation without such an analysis. I have experienced this, time after time, during my studies in Iceland when, in my notes, I was to give a name to an association. I was often uncertain as to how far I was now using the old, long-established terms "heaths," "fell- fields," "mat-herbages," etc., etc., with exactly the same meaning as the creators of these terms themselves gave to them. I did my best to use the correct terms, but I cannot deny that it often occurred to me, that it would have been much easier if the terms had been defined somewhat more precisely. For instance, had the term "heath" been defined as a plant-association in which dwarf shrubs or chamaephytes had a definite degree of frequency, it would have been far easier for me to have recognized the association in question, in the field: also remembering the fact, that the same association may perhaps be named sometimes in one way, and sometimes in another, according as the investigator in question received a more strong, subjective impression of this or the other species : It is pos- sible that a lichenologist would occasionally speak of a "lichen- heath," which a bryologist would call a "moss-heath," and a pha- nerogamologist an "E/npe/rum-heath" ! I see no other solution of the difficulty than that the investi- gator - - be he bryologist, lichenologist, algologist, phanerogamologist or what else, should define the association, as far as possible, from his own point of view, and then afterwards eventually agree upon how the whole association is to be named, and how the divergent names given by the investigators , may be reconciled with one another. In the following pages I shall define the associations according to the dominant growth-forms. I shall go through the chief plant- associations, adopting in the main the division briefly given by Thoroddsen in this work (vol. I, pp. 317 et seq.), from which, however, in some points I shall differ. Besides this analysis of the association as regards the various growth-forms it contains, there are several other matters which will be discussed, first among which comes the mass-occurrence of the different species, or growth-forms, contained in the association. Various methods have been used for this purpose ; they have been described and compared by C. Ferdinandsen (1918). Their 12* 1M) OLAF (1AI.L0E value varies greatly, and at the outset we may say that, for an exhaustive description, it is necessary to use several methods. Na- ture is too many-sided to be described in a few words, or by tabular methods. Among the chief methods may be mentioned Raunkiaer's valency-method (Raunkiser, 1916) which consists in the following: In an association a number of equally large sample-areas (e. g. 1 /io square metre) are demarcated, with equally large intermediate spaces between them, and the vegetation in them is investigated. Any plant-species (or any growth-form) which occurs in all the sample- areas is said to have the frequency-percentage (F. /o) 100, in half of the samples F. % 50, etc. By means of this method an idea is obtained of the frequency of the occurrence of the species (or growth-form) in the association. Investigators have also tried to express by figures the size of the space occupied by each single species, (or growth-form) in the area of the association; the mode of procedure is similar to that used in the determination of frequency, in so far that samples are taken, the area occupied by every single species in the sample is determined, and on the basis of this, the total amount of area occupied by the species in the whole association, is calculated. Lagerberg, Raunkiser, H. E. Petersen and C. Ferdinandsen recommend and employ this method (see these authors in the Bibliography). It is evident that it is very much to be wished, that we could give figures, which would be reliable for the areas occupied by the individual species. In the mean time it must be said, that the attempts made by the above-mentioned authors, to make such cal- culations, have proved an utter failure, and are quite worthless al- though, unfortunately, we must expect the method to be in vogue for some lime, and to be employed by others. The unreliability of the results obtained by this method, is due to the following fact: Even if we take a sample, ever so small, it is impossible to decide with any certainty how large a part of it is occupied by this or that species, unless it actually happens that only one species occurs in the sample. As soon as there are several species more or less entangled in each other, the conditions per- taining to the space occupied, are incapable of accurate description. How are we to determine, for instance, in a Danish C//H/ia-healh, how much of a sample is occupied by Calluna, and how much by LICHENOLOGY OF ICELAND 181 the reindeer moss entangled with it. The task is simply impossible, the question cannot be answered. The fact cannot be emphasized too sharply, that the figures which have hitherto been given for the areas occupied, and which have been obtained by the method of the above-mentioned authors, do not at all possess the numerical, the mathematical authority which numbers ought to have in order to be useful for purposes of statistical comparison. They are in short an illusion. Add to this, that even if the figures for the area occupied could be fixed fairly accurately, that would not give us any great knowledge of the abundance with which the species (or growth-form) in question occurs in an association. A ten-years-old beech-wood will frequently cover as large an area as one of a 100 years, whilst the figures for the area occupied would not give any idea of the enormous diffe- rence as regards masses in the two growths. It is true, anything like this need not be demanded of the figure in question, but then they are not very enlightening in any respect, and are therefore superfluous. In connection with the frequency percentage (F. %) (frequency- number), a far better method can be more advantageously employed, a method which science as far as I know has not employed very largely, but which practical men discovered decennia ago. It cannot be employed on excursions, with note-book and squared paper, or on expeditions on horse-back ; it requires a sojourn on the spot, and some patience. It is simply this: The mass of a wood is determined by the forester by its timber-contents in cubicmetres (it may be expressed in terms of weight!); the crop of a rye-field may be given in weight (straw and grain); and quite similarly could the natural vegetation of any place be treated by a man of science: but then it would be necessary to reap the plants, the masses of which are wanted to be known. This method has the advantage that - - of course in connection with other descriptive means (frequency-numbers, etc.) - it can be employed to characterize both the whole association, and its in- dividual species. Thus, it is really a valuable piece of information concerning an association, to know, for instance, that on a square metre there grow, on an average, let us say 2 kilograms of plants, while another association perhaps bears 200 kilograms. It must be admitted that this gives quite a striking impression of the plant- producing power in two such localities. I wonder how the tropical 182 OLAF GALL0E rain-forest, and the lichen-covered heaths of Iceland, would appear when thus compared according to relative weights of produce! It would be extremely interesting to ascertain. But also the luxuriance of the individual species or growth- form in an association, would he able to be characterized by this method. It would be very interesting to see, for instance, the result of comparing a piece of Danish heath with an Icelandic heath, in respect to the lichen-vegetation. How many kilograms of lichens each sample-area contains up there in the North and down here in Denmark. Unfortunately I have not been able to employ such a "weight"' method in my investigations in Iceland, nor had I at that time considered this matter more closely. But I am convinced that we have here an exceedingly valuable means of description, by which to characterize the difference between the masses, be it of the in- dividual species, the growth-form or the whole association; and, as already mentioned, practical men have long ago used it in pursuit of their object. a. The Deserts. Large tracts of Iceland have a desert-vegetation, i. e. a very open vegetation consisting of scattered individuals. Where to draw the boundary line between the desert and the closed vegetations, i. e. vegetations which cover the ground completely, is entirely a matter of opinion, and the boundary can only be an artificial one. We may for instance decide, according to Raunkiser's method, to take a large number of equally large sample-areas, and note down their vegetation separately. It will then be seen that many of the areas are entirely devoid of plants, and such areas may be designated (nil)\ and then resolve that a tract of land in which 75 % of the sample areas were devoid of vegetation, should be de- signated "desert. But, as already mentioned, whether this "per- centage of voidness" is chosen, or an entirely different one, for the designation "desert," it is and must be a matter of opinion. Such an analysis of "voidness" would be interesting for purposes of comparison, for instance between the Arctic cold-deserts, and the sub-tropical heat-deserts. But such an analysis has not yet been made, nor have the deserts of Iceland been, as yet, sufficiently in- vestigated in this respect. In Iceland many different kinds of deserts are found, the best- LICHENOLOGY OF ICELAND 183 known are the fell- fields of the plateaux; but others exist also, as for instance vast sandy tracts with drifting sand, both in the highlands and in the lowlands. We shall now consider these deserts more closely, leaving out those with a rock-substratum, which will be discussed elsewhere. According to the substratum we can divide the deserts into stony, gravelly, sandy and clayey deserts. A division according to the principles of plant-ecology, cannot be undertaken, as the vege- tation has not been sufficiently investigated, from a statistical point of view. Stony Deserts are the stone-covered ridges (holt) of the lowlands, and the talus of fallen blocks and debris (Urd) of the highlands. The lichens growing directly on the stone-substratum, do not concern us here, but between the stones on the ridges there grow as chasmophytes, Dryas octopetala, Thymus Serpyllnm, Silene acaulis, Potentilla verna, Cerastium alpinum, Arabis petrcca, Saxifraga ccespitosa, Juncns trifidns, Luznla spicata, Achimilla alpina, Poa glauca, Elyna Bellardi, and a number of less frequent species (according to Jonsson). Interspersed in the moss- car pets occur (according to Jonsson's list in "Vegetationen paa Snaefellsnaes," p. 41) the fol- lowing species: Cladonia rangiferina (podetia- wandering fruticose lichen). Thamnolia vermicularis Cladonia uncialis Sphserophorus coralloides Cetraria aculeata Sphaerophorus fragilis Cladonia pyxidata (hypothallus-wandering fruticose lichen). cornucopioides Cetraria islandica (erect foliaceous lichen). Peltigera canina (horizontal foliaceous lichen). rufescens aphtosa Jonsson does not mention having found any crustaceous lichens, therefore these will hardly occur in conspicuous abundance, whilst it may be expected that, on future investigations, some or other of the small, inconspicuous species may be found, at any rate on decaying moss. Jonsson also mentions the fact that here and there Cladonia and Spharophorns spp. may occur as dominants in a sub-vegetation of mosses, in addition to more sparsely occurring Graminece. The taluses of fallen blocks and debris (Urd) in the 184 OLAF GALL0K highlands, are either very poor in, or entirely devoid of, phanero- gams, and between the stones mosses idriinmia hijpnnides) chiefly occur, in part together with lichens; this will, however, be discussed more fully under the vegetation of the moss-carpets of the island. The Gravelly flats in the lowlands bear a scanty vegetation of herbs, (see e. g. Thoroddsen in vol. I, p. 326 of the present work; Jonsson's lists are exhaustive, but, like Thoroddsen, he makes no mention of linding lichens). In river-gravel in the lowlands Chamcenerium is common. The river-flats are occasionally inundated in spring, and are devoid of lichens. The gravelly flats of the plateau are "the parts of the rocky flat poorest in plants" (Jonsson). Here and there grow Luzula spicata, Oxyria diyyna, (lerastium alpinnm, Silene acaulis, Arabis />elrcea, Galium silvestre, Saxifraga ccespitosa, etc. Moss-cushions (Dicranum falcatum) occur also, and, - - as "collars" around larger stones, - - small carpets of (irinuuia hypnoides intermixed with lichens (C.clraria islaiidica and CAadoma) and phanerogams; this will be mentioned more fully under the moss-vegetation. The gravelly flats which I traversed just below the summit of the mountain "Sulur, near Eyjafjordur, were still, on the 5th of July, supersaturated with the down-trickling snow-water, and were quite bare of vegetation. Sandy flats. Several kinds of sandy flats of various geological origin occur, partly in the lowlands, and partly in the highlands. Many of them are quite bare of plant-growth along such great tracts, that days intervene before a few individuals are again met with. The commoner types of sandy flats are: beach-sand (with a halo- philous herb-vegetation), which is devoid of lichens (owing to its contents of chloride of sodium); Jokul-sand (which is often inundated by Jokul-rivers) either devoid of, or with a very poor, herb-vegeta- tion, and without lichens (on account of inundations possibly fol- lowed by drifting sand); and lastly tracts of blown sand (Sander) of various origin, but more or less wind-affected on the surface by frequent and violent sand-storms. The diflerent kinds of sand men- tioned here are devoid of lichens, owing to three essentially different reasons: (1) the occurrence of chloride of sodium in the soil (beach- sand), (2) frequent inundations (the sandy tracts below the Jokuls) or (3) drifting sand, (in the sandy tracts of the plateaux and else- where). I traversed, in several places, such extensive sandy tracts, as LICHENOLOGY OF ICELAND 185 for instance Holasandr (north of Myvatn), the '"Sanders" in the delta of the Jokulsa (at the head of AxarfjorSr), and the dunes between MVvatn and the Jokulsa. The first of these tracts (Holasandr) consists of black sand, in which are numerous stones with worn edges. It is very poor in vegetation; there occurred however, scattered uniformly over the entire surface, some grass, in tufts, at stated intervals of about l /s V-2 metre. All other kind of vegetation was absent, for instance owing to the strong sand-drifts prevailing everywhere - - not a single moss or lichen was found. As mentioned above, the stones were highly worn by the action of sand, and bore no mosses and hardly any lichens; scarcely a hundred out of the thousands of stones I passed by during a two- hours' ride, bore any vegetation at all, and even that of these few stones was extremely scanty. The following species were found : - Stereocaulon spp. (fruticose lichen). Parmelia lanata (foliaceous lichen). Gyrophora arctica erosa Lecidea pantherina (crustaceous lichen). The dune terrain east of Myvatn bore in numerous places a scattered vegetation of Ely inns arenarins, which looked very remark- able against the dark background of black sand. Here also strong sand-drifts prevailed, and the ground was, in consequence, quite devoid of lichens. As regards their vegetation and other external conditions, the blown-sand areas in the delta at the mouth of the Jokulsa, greatly resemble, for instance, Holasandr. The sand, which is mixed with stones with worn edges, drifts very much. In stormy weather it was not possible for us to see even a few hundred metres in front of us on account of the sand-clouds, which filled the air near the ground. In this place, a little grass, some Silene acanlis, and a few other phanerogams, formed an extremely poor and scattered vege- tation. Mosses and lichens were totally absent, on account of the drifting sand. Desert-like, clayey-flats with a poor or scattered vegetation, have been described more fully by Jonsson from East Iceland, Snaefellsnses and South Iceland. They are, however, frequently more luxurious, and can bear a vegetation which forms a kind of transi- 186 OLAF GALL0E tion to heath-vegetation. An instance of this is also given below under the description of heaths (Type III). We shall elsewhere - - under the description of Iceland's moss- carpels and their lichens, - have an opportunity of discussing the competition between moss and lichen. Here it will suffice to state, that lichens, in the loose soil of mountain -bights, in mountain- deserts, rarely occur on quite bare, purely inorganic soil. They show a peculiar tendency to seek company with mosses or other plants, without its being always possible to state precisely, which have been the first to arrive on the spot. The species which appear to be most common on loose soil in mountain-deserts are the following: Cladonia turgida (fruticose lichenX frequently sterile. pyxidata , on humus, rangiferina cocci fera Stereocaulon denudatum - Alectoria nigricans Thamnolia vermicularis - , sterile. Cetraria hiascens (foliaceous lichen), frequently sterile, islandica Fahlunensis aculeata (fruticose lichen), Solorina crocea foliaceous lichen), Pannaria microphylla Peltigera aphtosa lepidophora Dermatocarpon hepaticum - , on moor-soil. Lecanora tartarea (crustaceous lichen), fertile; on moss, moor-soil and lichens. Bacidia flavovirescens (crustaceous lichen), often sterile; on purely inorganic soil. Pertusaria oculata (crustaceous lichen), often fertile. Buellia parasema v. papillata, fertile ; on moor-soil, v. triphragmia, fertile, liinodina mniaroea (crustaceous lichen) v. cinnamomea, fertile; on moor-soil. Lecidca assimilata crustaceous lichen), fertile; on dead moss. C.nloplaca Jungermanniae , fertile; on moor-soil. I'soroma liypnorum . fertile: on moss. Lecanora caslanea . fertile; on moor-soil. r,;ioiii\ ces hyssoides , often sterile; on moor-soil rich in miner;:!. LICHENOLOGY OF ICKLAND 187 This is by no means an exhaustive list of the earth-lichens of the plateau; it must be supplemented by several other species, the occurrence of which is not known very accurately, and also by some which will be mentioned under the description of the moss- carpets of Iceland; these, as we know, partially extend upwards into the most desolate wastes of mountain heights, and are there found interspersed with various species of lichens. b. Lichen-heaths of wide extent do not appear to occur in Iceland. In the above a couple of instances have been mentioned showing that lichens can, in patches, dominate the physiognomy of a Grimmia-carpei or of a poorly-developed chamsephyte-heath. But beyond this, no lichen- heaths proper are known, as they are described from other places in Arctic Regions. c. Moss-vegetations. Whilst chamaephyte-heaths, grass-areas and coppices all have their own fairly distinct horizontal limits, this is not the case as regards the moss-areas. These are found at all altitudes, right up to -the snow-limit, both in the low land and in the highest plant- bearing high land. The moss-vegetation itself has been exhaustively described elsewhere in this work (Hesselbo, 1918). I shall there- fore occupy myself exclusively with those parts of it which are of importance to lichen-growth. Mosses differ (in a higher degree than do lichens) in their re- quirements as regards moisture, in that several are hydrophytes (Fontinalis, Sphagnum spp., etc.), whilst others suffice with intermit- tent supplies of water, and some are distinctly xerophytic. The vegetation of all areas of perpetual water-containing mosses, (in bogs and the like) is always devoid of lichens. Here therefore, only that vegetation will be discussed which, during a shorter or longer period of the year, is dry and contains lichens. This refers, consequently, almost exclusively to the Grimmia- vegetation in both the high and low land. But before mentioning these more closely I shall say a few words about the Philonotis- bogs on the mountain slopes. They are seen in the landscape as bright-green patches on mountain declivities, where springs appear on the surface of the ground, and are extremely common every- o */ */ INS OLAl (1AI.L0E where along the sides of the fjords. Owing to their great water- contents they are always devoid of lichens. Grimmia-heaths are found, as mentioned, at all altitudes right up to the sno\v-line, but differ somewhat according to the altitude. The substratum which supports the f//'//mm'a-carpet is some- times solid rock, sometimes loose soil. Mv own observations are KI derived almost exclusively from carpets upon lava. On mountain heights (fell -fields) the carpets are often small in extent, but further down in the low land they may cover large continuous tracts. The plant-carpet is a few centimetres high and the moss-shoots stand erect. Whatever may be the nature of the deeper-lying sub- stratum, at the bottom of the carpet there is always found, as a matter of course, a peat-formation consisting of the dead remains of the mosses, as soon as the moss-covering is only a few years old. The deeper-lying soil is evidently of no direct importance, or concern to the lichens; they are connected with the peat and the dust-particles, which always occur on it, and amongst the mosses. With regard to the amount of w r ater contained amongst the mosses, very little is mentioned in the literature. It may, however, be taken for granted that all Grnmm'a-vegetation in Iceland is dry enough to bear lichens. My own observations show this distinctly enough. For the rest, there is, as usual, the great defect, that we h:ive no fixed method to indicate the degree of dampness of the plant-association, as far as emergent associations are concerned. We are constantly reduced to the entirely relative, and consequently almost useless terms, "dry," "damp," etc., without any fixed state- ment as regards measured amount. Jonsson states that there is an essential difference in the ac- companying phanerogams in high and in low land, in that only a lew occur on the rocky flat, whilst they are found far more numer- ously further down. He states, in addition, as a general fact, that lichens are found more abundantly in the (iV/m/ma-carpets of the rocky flat, than in those of the low land. How far this is quite right can only be proved by frequency-numbers, and statements of mass-occurrences (in weight), and such are not found in sufficient numbers. I must, however, say that Jonsson's statement sounds \ery reasonable, and is supported by Hesse Ibo. It can undoubtedly be explained by the fact that the climatic conditions are more un- favourable to the mosses in the high land, and relatively more LICHKNOLOGY OF ICELAND 189 favourable to the lichens. Whether the absolute amount of lichens (in weight per unit of area) is really greater in the high land than in the low land is perhaps doubtful. But there is nothing to prevent the assumption that the amount, in proportion to the mosses, is greatest at a high altitude, not because the climate of mountain- heights is favourable to lichens, and is more agreeable to them than the climate of the low land, but because it is more inimical to the mosses than to the lichens, and thereby causes the latter to grow in apparently greater luxuriance. It is absolutely necessary to warn against a too strong belief in one's first-hand and direct impression as regards this matter; only actual measurements can give real information. As an instance of a decided (irimnua-healh I shall describe more fully a stretch of land near Havnefjord (South-west Iceland). The substratum is an older lava-field consisting of highly vesi- cular and porous post-glacial lava, the surface of which varies greatly, in that there occur level plains of small-sized lava-debris, strewn here and there with a little soil, large blocks of rock of varied appearance, vertical faces of rock, and caves, all mixed together in great confusion. The Grimmia- carpet extends chiefly over the level plains covered with lava-debris. An enumeration of the characteristic plants gave the following results : Grimmia occurred in all the sample-areas (F % 100), crustaceous lichens (F % 65), fruticose lichens (F /o 15), bare ground (F /o 10), grass (F % 65), Galium (F % 60), and some Silene acaulis. The numbers may lead us to believe that crustaceous lichens highly dominate the plant-physiognomy of the carpet; this is, how- ever, not the case. The following species of lichens have been found : Cetraria aculeata, fruticose. Pertusaria corallina, crustaceous. Cladonia coccifera, Sterile crustaceous lichens. But several other species may occur. If we enumerate all the species which have hitherto been recorded, we get the following: Alectoria ochroleuca v. cincinnata, podetia-wandering fruticose lichen. Cladonia rangiferina, Thamnolia vermicularis, Cladonia uncialis, I'.IO OLAF GAI.L0K Stereocaulon denudatum. podetia-*wandering f'ruticose lichen. Sphserophorus fragilis. coralloides Cetraria aculeata, Cladonia pyxidala, hypothallus-wandering fruticose lichen. gracilis, cornucopioides, Cetraria islandica, erect foliaceous lichen. Peltigera canina. procumbent foliaceous lichen. rufesceus, aphtosa, Solorina crocea, Pertusaria corallina. crustaceous lichen. Sterile crustaceous lichens. Altogether about 18 species. Quantitively, as far as it appears, the fruticose lichens are decidedly dominant in some places. Thus, Jonsson has seen them in such abundance amongst Grimmid. that he calls them "indicative of Lichen-heaths." But this appears to be only true of patches here and there. I myself have not met \vilh this phenomenon. In Denmark we have nothing that can be compared with the Icelandic Grimmza-carpets, as regards superficial extension. Where we, here and there, find Grimmia-bogs scattered in our heaths, they are generally small, and appear to be wetter at the bottom, than are those in Iceland, and are consequently practically devoid of lichens. The difference no doubt chiefly de- pends on the fact, that in Denmark the Grimmia-bogs usually occur in damp hollows, where stagnant ground-water furnishes them with the necessary moisture, whilst the Grzmmia-carpets in Iceland are, in a higher degree, directly furnished with this by rain. The C/r//mn/a-carpets in Denmark have, as a rule, undoubtedly a quicker vertical growth, and deeper peat-substratum, which explains the characteristic paucity of lichens in our Grun/nza-carpets, and the lichen-wealth in those of Iceland. It is consequently, in the first instance the competition which is stronger and more inimical to lichens in Denmark than in Iceland. Besides this, it is strange that the Iceland <7r/ni/ma-carpets can contain quantilively, such an abundance of crustaceous lichens, whilst ours are quite devoid of them. A Table will render the difference plain: LICHENOLOGY OF ICELAND 191 Fruticose Foliaceous Crustaceous Number lichens lichens lichens of species Icelandic Grimmia carpets . . 61 % 28 % 11 ), 5 foliaceous lichens (21 %) and 8 crustaceous lichens (33 /o). Here, as in the case of the heath, is a want which has not yet been supplied; the mass-occurrence (given in weight) of the lichens has not been determined. Nor is the average frequency- number known, for reasons which have been mentioned above. It is therefore difficult to give any comparison between the lichen- vegetation of the grass-areas of Denmark and Iceland, as regards quantity, so far as this is manifested by mass-occurrence and fre- quency-number. As regards quality, i. e. with respect to growth-form and systematic species, a comparison can more easily be made. 13* 196 OLAF GALI.OI It must be borne in mind that Iceland is peculiar owing to its great abundance of natural, free-growing pastures, both damp meadows, devoid of lichens, and drier lichen-bearing areas, whilst Denmark is almost devoid of uncultivated pastures, for damp mea- dows are frequently more or less cultivated (drained, etc.), and most of the other grasses are under intensive culture, entering into the regular rotation of crops. Consequently, the lichen-bearing areas in Denmark are very small and contain, according to my observations, only about 16 lichen-species, vi/. 12 fruticose (CAadonm rangiferina, C. rangiformis, C. uncialis, C. furcata, C. gracilis, ('.. s(]iiamosa, C. pyxidata, C. fimbriata, C. Floerkeana, C. cocci fera, (lelraria aculeata, and Stereocanlon paschale), 2 foliaceous (Cetraria iiivalis and Peltigera canina) and 2 crustaceous (Sphyridiu.ni byssoides and Lecidea uli- ginosa). The relationship according to percentage is consequently as follows: Fruticose Foliaceous Crustaceous lichens lie lens lichens Danish lichen-bearing grass-areas (in dunes, etc.) 75 /o 13 /o 13 /o Icelandic 46 /o *21 /o 33 % As seen from the lists, the species are not the same, although several are common to both countries. But the most conspicuous difference is that which has regard to the growth-forms, Iceland having a very great number of crustaceous lichens - - which appear to play rather an important part as regards the plant-physiognomy viz. 33 %>. This undoubtedly indicates that the competition between grass and lichen results rather in favour of the lichens in Iceland, than of those in Denmark; that is to say, the presence of the great number of crustaceous lichens is not due either to climate or soil, but to a less keen competition. Consequently, if we are to sum up in a few words a comparison between the lichen-vegetation of the Danish and Iceland grass-areas, we must say, that Iceland has the greater number of species, 24 as ;ii>ainst 16 Danish, Iceland has 11 fruticose lichens, ."> foliaceous lichens, and 8 crustaceous lichens, while Denmark has 12, 2, 2 LICHENOLOGY OF ICELAND 197 respectively. The numerical preponderance as regards Iceland is due to the foliaceous and especially the crustaceous lichens. The mass-occurrence (in weight) in both countries is unknown, as is also the frequency-number in both countries. For a first-hand and direct consideration the difference does not appear to be great in these two respects, but we ought not to remain standing at this point. e. Heaths. Under this name I include all such associations as are identified in the field by the fact that all, or at any rate almost all, the sample-areas contain chamsephytes, mainly dwarf-shrubs. A phanero- gamologist will hardly suffice with so short and summary a cha- racteristic, and it is his task to investigate partly which growth- forms the heath contains, and what percentage of each (chamse- phytes, hemicryptophytes, etc.) and partly what frequency -degree each of these growth-forms has. A vegetation of which some of the sample-areas contain Empetrum only, others Calluna only, and others again a mixture of both is, according to the diagnosis used here, a heath as entirely as a vegetation which contains exclusively Calluna in all its sample-areas, because Calluna and Empetrum belong to the same grow T th-form. When I here mention as a kind of diagnosis, the characteristic that all or almost all the sample- areas must contain some or other chamsephyte, this should not be regarded as an analysis of the phanerogamic growth-forms of the Iceland heath such will no doubt be given elsewhere in this work but it is simply an easily recognizable feature whereby one can perhaps in the future recognize such Icelandic vegetations, of which the lichen-vegetation has been investigated by me and will be described more fully later on in this paper; in a similarly sum- mary manner phanerogamologists describe lichen-vegetations, moss- vegetations, etc. in associations which interest them for the sake of the phanerogams. It is in addition a diagnosis of quite similar character as the diagnosis that a wood is an association in which every sample-area contains a tree or parts of a tree a diagnosis which does not involve anything whatever as to the entire biologi- cal aspect of the wood, when all its species are enumerated according to their growth-form. I must add, that in the investigation of the heath-associations, I took, in the majority of the localities, sample-areas of 2 square 1 ( .)S OLA I' GALL0E decimetres (dm. 2 ) with intermediate spaces of equal si/.e, viz. about 1 metre. The majority of the heaths, regarded as landscapes, are easily recognizable in Iceland by their greenish-brown tone of colour, which makes them conspicuous even at a fairly long distance. They occur on mountain-sides up to a height of about 400 metres. It is stated that on slopes (mountain-sides) the ground and hence also the plant-covering is flat, whilst they are knolly and uneven on a horizontal substratum. These features agree exactly with my observations. In the following I shall give some examples of the more fre- quent fades of the heath and their lichen-vegetation. Type I. Dry heaths on level (not knolly) ground. (a) Heaths rich in phanerogams but either poor in or devoid of lichens. Near Hals parsonage in Fnjoskadalur (North Iceland) I noted down that there occur extensive heaths the character plants of which are Empctnim, Betula nana and various Glumiflonv, mostly grasses. Each of these occur in all the sample-areas, i. e. they have the frequency-percentage 100. The ground, which is gently sloping, consists of line, reddish sand, and is covered by a continuous carpet of the above-mentioned character-plants and by a few others which have a lesser frequency-degree, e. g. Dryas, Silene acaulis, etc. Both the open ground and the birch- clusters are de- void of lichens. The reason of this phenomenon merits fuller discussion. As mentioned above, we can, on the whole, point out eight essential factors which determine the presence or absence of earth-lichens in a particular association, viz. the chemical composition of the soil, the size of its grains, thermal conditions, water-contents, drifting soil, burrowing animals, a layer of decaying leaves, snow-covering, and competitive relations with other plants. Among these eight factors we must consider more fully the layer of decaying leaves and the competitive relations with neighbours. It is impossible to believe that all the other factors mentioned above, could have an injurious influence on a lichen-covering on the heath-areas in question. But the two powerfully acting factors just mentioned are without doubt instrumental in the existing want of lichens. The fact is, that dwarf-birches, where they form dense growths, are fairly high in growth, cast rather a deep shade, and shed a considerable number LICHENOLOGY OF ICELAND 199 of leaves which cover and choke such lichen-germs as might pos- sibly fall on the plant-carpet and try to hold their own there. The frequency-percentage (100 %>) of the dwarf-birch in this association does not, as a matter of course, give us any idea of the fact that it dominates the area to such a high degree and has such an exclusive influence as regards the lichens. It has not for instance a higher frequency-number than have the Empetrnm and Gramineie in the same association. Yet we shall see further on that both Em- petrnm and Graminece in purer growths i. e. not at all or only slightly mixed with birches - - are far more hospitable towards the lichens than is the association described here, whose want of lichens must therefore undoubtedly be attributed to the presence of the dwarf birch. In itself it is a drawback of the method in question, that this quality cannot be deduced from the frequency-number - that the latter expresses so imperfectly the area covered by the species pre- sent; but I fear that this drawback will ultimately be found to be insurmountable, whatever method should be adopted. The word- description of the association must here supplement the statistical figures. I found heaths of this kind or of very much the same com- position on extensive tracts between the farms of Hals and Einar- staSir, lower down on the mountains; especially in Fljotshei5i, a locality near the latter farm, I noted down a vegetation of dwarf- birches (F % 95), i. e. frequency-number 95, Empetrum (F % 90), Glumiflorce (F % 85), Vacdmum uliginosum (F % 65), Dryas (F % 45), 'Salix lanata (F %> 30) and Calhuia (F % 10). The dwarf-birch was consequently somewhat less frequent and a little less dominant there. A few other species grew scattered in the plant-carpet, and there occurred also a small quantity of lichens, F % 20 (10 /o cru- staceous lichens, /o foliaceous lichens, 10 % fruticose lichens) and a small quantity of mosses (F /o 5). The lichens in question were Alecloria ochrolenca and Tham- nolia vermicularis, both podetia-wandering fruticose lichens, and a few crustaceous lichens which were not determined more closely. In large, extensive tracts of land along the left bank of the Jokulsa, and between the farms of Svinadalur and As, I observed heaths somewhat more luxuriant in composition and characterized by an abundant mixture of Salix lanata. The other species were Betula nana (F /0 100), Glumiflora* (F /o 100), Empetrum (F , o 95), 200 OLAF GALL0E \'ficcininm uliginosum (F /o 80), Sali.v lanatd (F /o 60), Geranium silvaticnm (F % 26), Betula pubescens (F % 20), Sali.i- spp. (F % 20), l-: 100), Glumiflorcc (F % 100), dwarf- birch (F % 50), Empetrum (F % 40), Salix lanata (F % 20), and Vaccinium nliyinosnm (F % 20). Peculiar to this heath was the total absence of lichens, which was evidently due to the shifting soil of the place in question, strong winds causing it to drift. It was evident that the plant covering and other conditions were not de- trimental to the lichens, which in other places throve excellently among the same competitors which occurred here. Thus we have seen two essentially different factors which may be instrumental in excluding a lichen-vegetation from heaths; (1) certain shade-casting, deciduous chamsephytes and Nano-phanero- phyles which may dominate so highly that lichen-growth is made impossible, and (2) drifting soil which may play exactly the same part, even if the plants present are not in themselves any hindrance lo lichen-growth. Type I. (c) Heaths poor in phanerogams and rich in lichens. Other heaths may be rich, even very rich, in lichens. We shall now mention some specimens of them. In the healhs near Einarslaftir (Adalreykjadalr in North Iceland) were found scattered larger and smaller areas of Dryas-grass- heaths which were easily discernible even from a considerable LICHENOLOGY OF ICELAND 201 distance owing to their light greyish-green tone of colour. Their character-plants were Drijas (F /o 100), Glnmiflorce (F /o 100) and Empetnim (F /o 90), besides less important quantities of dwarf- birches (F /o 10) and Silene acanlis (F /o 10). As indicated by the names, the plant-covering is rather low; the soil was stable (not drifting) and no abundantly leaf-shedding plants were predominant in it. Such areas were peculiar by the vegetation being also phy- siognomically highly dominated by lichens, especially crustaceous lichens, for lichens, taken as a whole, were found in all the samples (F /o 100). Fruticose lichens (F % 100), do not play any dominant part physiognomically, in spite of their high frequency-percentage (F /o 100), that is to say, they are not very conspicuous as masses. This is in a way also true of the foliaceous lichens (F % 33), whilst crustaceous lichens (F /o 100) are dominant to an unusual extent. This is a very peculiar feature, as it must be remembered that crustaceous lichens, taken as a whole, have very great difficulty in holding their own amongst other competiting plants, for they are very easily choked by being even very slightly covered over by larger neighbours. Taken as a whole, the association just described may be regarded as a characteristic Arctic association, poor in phanerogams and rich in lichens. The following species occurred: Fruticose lichens Foliaceous lichens Crustaceous lichens F% Fertile o 'E ii *- v: Cetraria aculeata -u 100 4- Alectoria ochroleuca 4- 100 4- Thamnolia vermicularis 4- 4- Cetraria islandica + 20 4- Solorina saccata l__ 10 4- Leptogium lacerum 4- i 4- Peltigera lepidophora 4- 4- Lecanora tartarea 4- 100 i 4- Bacidia flavovirescens.. . 4- i 4- Caloplaca pyracea 4- , ' 202 OLAI- GALLOK Consequently, 3 sterile fruticose lichens, 4 f'oliaceous lichens (of which 1 sterile) and 3 crustaceous lichens (of which 1 sterile). * In the districts around Myvatn about Hlidarfjall I noted similar /Jn/as-heaths covering large tracts alternating with bare sand. Here the characteristic plants were also Dry as (F /o 100), Empelnim (F %> 100), Glnmiflorce (F % 100) and abundance of dwarf-birches (F o 7(1) and Vaccininm nlit/inosnm (F % 50). What has been said above about the factors which conditioned the life of the lichens in the heaths near Einarsta5ir holds also good as regards these heaths. A fairly rich lichen-covering occurred (F /o 100), viz. fruticose lichens (F % 100), foliaceous lichens (F /o 50) and crustaceous lichens (F % 90); but, as may be seen, the larger species preponderate slightly, perhaps in correlation with the fact that dwarf-birches are more dominant here and determine the character of the lichen-vegetation. The following species were found : - s. 7 !0 C 'S. ^ if c 3 ~ ' _0 o *3 J: el - F/o t u .~ - u *-* i~ o -~ 3 '= &H c ~ Cetraria aculeata 4- 100 4- Alectoria ochroleuca 4- 90 4- Thamnolia vermicularis 100 4- Alectoria nigricans 60 4- ' Cladonia rangiferina . 4- 10 4- Cetraria nivalis 4- 30 4- islandica 4- 20 4- Lecanora tartarea 4- 90 4- Consequently, 5 fruticose lichens, 2 foliaceous lichens and 1 crustaceous lichen. The species of lichens are not everywhere the same, but they do not vary greatly. In the neighbourhood of Mvvatn I traversed large tracts of heath, still poorer in phanerogams, where the fre- quency-percentage of the lichens was very great (F % 100) and where the landscape displayed dark patches of blackish-brown lichens (Celrarid isldiidicd, (]. niyricans and C. cornicnlata). Here we might perhaps be justified in speaking of "lichen-heaths," but I think that their contents of Dryas, F /o 100, make such a name superfluous. LICHENOLOGY OF ICELAND 203 I shall describe one more specimen of a Dryas-heaili which I investigated near EinarstaQir. The ground was slightly inclined and partially bared in many places. The plant-covering was 8 10 cm. high and consisted of Dryas (F % 100), Empelrum (F /o 100), grasses (F /o 100), dwarf-birch (F % 64), Azalea procumbens (F % 24), Vac- cinnm uliginosum (F % 16), Polygonum inmpamm (F % 12) and Tha- lictrnm alpiiinm (F % 4). In this low-growing, open vegetation a quantity of lichens was growing (F ,o 100), frulicose and foliaceous lichens and Lecanora tartarea. The species were: Alectoria ochroleuca (fruticose lichen). nigricans Cetraria nivalis (foliaceous lichen), aculeata (fruticose lichen). Thamnolia vermicularis (fruticose lichen). Lecanora tartarea (crustaceous lichen). The types of heath described above are characterized by their level, partially sloping substratum, their open and low-growing ve- getation, and chamsephytes and hemicryptophytes with slight leaf- fall which dominate, both physiognomically and ecologically. Con- sequently, the conditions are favourable to the lichens, and their frequency-percentage is everywhere 100 or thereabout, sometimes crustaceous lichens (mostly Lecanora tartarea}, sometimes fruticose lichens dominating. Type II. Dry, knolly heaths with phanerogams on the hori- zontal surface of the knolls, lichens on the sides of the knolls, and mosses, etc., in the narrow depressions or ruts between the knolls. A third type of heath which is common in Iceland is the Knolly heath; it has fewer lichens than has the low-lying, level Dryas-Empetrum-grass-heaih. I noted some examples of this type of heath from different areas in North Iceland between Einarsta9ir (in ASalreykjadalur) and Myvatn, on Reykjahei5i (south of Axarfjor5ur, between the Jokulsa and the Laxa), along the left bank of the Laxa (which runs out into Skjalfandi) and in a few other places. As already mentioned it is peculiar to these heaths that the ground is very knolly, i. e. it consists of mounds with deep inter- vening depressions. The heaths appear usually or perhaps exclu- sively to develop on level (not sloping) ground. Between Einarstadir and Myvatn (in the valley of the Laxa) heaths were found composed of Empetrum (F % 100), grasses (F % 100), dwarf-birch (F % 80), and a few other phanerogams with a 204 OLAF GALL0E considerably less frequency-degree and physiognomical dominance. Lichens were found in all the samples (F % 100), but nevertheless played physiognomically a less considerable part than in the level Dryas-grsLSS-Empetrum-healh. They all occurred on the sides of the knolls, while the horizontal surfaces of the knolls were covered by phanerogams. The following species occurred : o ' ous s eo ns |l 1 1 F r OLAF GALL0E similar to that in Reykjaheidi. The dominnnt phanerogamic vegeta- tion upon the knolls consisted of Empelruni, grass and together with small quantities of dwarf-birch, Arctost(i}>ln/los nrsi, Betuln nana, Vaccininm nliin/>e luipuuides (F /o 45), Akhemilla alpina (F" / o25) and a few others which were not very conspicuous (e. g. Azalea ]>rocnmbens, LICHENOLOGY OF ICELAND 209 species of Salix, etc.); there occurred also a small amount of mosses (F % 20), and some lichens (F % 45). It was distinctly seen, that here all vegetation, both phanero- gamic and cryptogamic, was greatly retarded by the long-lasting snow-covering, and by the fact that the soil was very wet and cold during the growth-period. The following -species occurred : Stereocaulon spp. (poorly developed) (fruticose lichen; sterile). Peltigera rufescens (foliaceous lichen; sterile). aphtosa ). lepidophora ( ). Leptogium lacerum ( ; ). Psoroma hypnorum (crustaceous lichen; fertile). In order to obtain a general view of the subject, some typical tables are given here in w r hich the different kinds of heaths are presented in tabular form. They are resumes of the preceding text. Type I a. (Dry heaths on level (not knollyl ground; rich in phanerogams; devoid of, or poor in, lichens). Ex. 1. Heath near Hals parsonage (North Iceland). Dwarf birch F /o 100 Dryas (a small amount) Empetrum F % 100 Arctostaphylos. (a small amount) Grasses F % 100 Lichens F /o Ex. 2. Heath between Svinadalr and As (North Iceland). Dwarf birch F /o 1 00 Salix spp F % 20 Glumiflora; F /o 100 Equisetum F % 20 Empetrum F % 95 Calluna F % 7 Vaccinium uliginosum . F /o 80 Lycopodium F /o 7 Salix lanata F /o 60 Mosses F % 13 Geranium silvaticum.. . F % 26 Lichens F o Betula pubescens F /o 20 Ex.3. Heath near Einarstadir (North Iceland). Dwarf birch F % 95 Dryas F % 45 Empetrum F , o 90 Salix lanata F /o 30 Glumiflorae F /o 85 Calluna F /o 10 Vaccinium uliginosum.. . F , o 65 Lichens F % 20 The Botany of Iceland. Vol. II. 14 210 OLAF GALL0E Type I b. (Dry heaths with drifting soil; devoid of lichens Ex. 1. Heath on mountains between Fnjoskadulur and Ej'jafjordur (North Iceland). Dryas F /o 100 Salix lanata F /o 20 (ilumillorre F /o 100 Vaccinium uliginosum . . F /o 20 Dwarf birch F /o 50 Lichens F o Empetrum F , o 40 Type I c. (Dry heaths on level (not knolly) ground; heaths poor in phanerogams. hut rich in lichens). Ex. 1. Heath near Einarsta5ir (North Iceland). Dryas F /o 100 Dwarf birch F /o 10 Glumiflorte F % 100 Silene acaulis F " o 10 Empetrum F % 90 Lichens F o 100 Ex.2. Heath near Myvatn (North Iceland). Dryas F /o 100 Dwarf birch F "/o 70 Kmpetrum F /o 100 Vaccinium uliginosum . F o .~>0 dlumiilore F o 100 Lichens F /o 100 Type II. (Dry, knolly heaths with phanerogams on the horizontal surfaces of the knolls, lichens on the sides of the knolls, mosses, etc., in the depressions between the knolls Ex. 1. The vegetation of the knolls on the heaths near the Laxa (North Iceland). Kmpctrum F o 100 Dwarf birch F o 80 Grasses F o 100 Lichens F o 100 Ex. 2. The vegetation of the knolls on the heaths near the Laxa, near Skjalfandi. Calluna F /o 100 Dryas F /o 40 Kmpelrum F o 100 Dwarf willow F /o 20 7 /o of the heath-lichens), 3 foliaceous lichens (8 %>) and 13 cru- staceous lichens (35 %), in Iceland the proportions of growth-forms are distributed as follows:- 15 are fruticose lichens (33 %), 11 are I'oliaceous lichens (24.5 /o), and 19 are crustaceous lichens (42 %). LICHENOLOGY OF ICELAND 215 The Growth-forms of the Heath-lichens. Fruticose Foliaceous Crustaceous Number of species Danish heaths 57 % 8 % 35 % 37 Icelandic heaths. . 33 % '24.5 % 42 % 45 Of these numbers the Danish will scarcely be altered to any extent, whilst the Icelandic, through more numerous and more de- tailed investigations, will probably undergo a very radical alteration in favour of the crustaceous lichens. On riding across the heaths in Iceland it strikes one that the crustaceous lichens are more do- minant there than in Denmark. This agrees closely with the fact that the chamsephytes are, as a rule, obviously poorer and less well- developed there than on Danish heaths, and are consequently more hospitable towards lichens, than are the taller, well-grown species. With respect to the frequency-number of the lichens, none are to hand from Denmark. Those from Iceland are given above. Judging from what I remember, and compared with what I wrote on the subject in "Danske Licheners 0kologi" (p. 301 et seq.), I am, however, inclined to believe that in Denmark all possible frequency- numbers occur, from to 100, as in Iceland, in that we have in Denmark Ca//H/?a-heaths, which are sometimes very rich in lichens and sometimes almost devoid of them. In this respect there is scarcely any difference worth mentioning between the Danish and the Icelandic heaths. It is as difficult or, properly speaking, still more difficult to state anything about the mass-occurrence of the lichens in Denmark com- pared with Iceland. I must, however, enter somewhat more closely into this question, as it is, in addition, of more far-reaching eco- logical importance. If we are briefly to compare Iceland and Denmark as regards their lichen-vegetation on heaths, as far as this can be done on the basis of the investigations hitherto made, which in a high degree require to be more detailed as regards both countries, especially with reference to the mass-occurrence of the species, it may be stated that: OLAF GALL0E The heaths of Iceland and Denmark, regarded from the point of view of a landscape, resemble each other as regards their whole physiognomical feature, besides which there is a great similiarity as regards the frequency- degree of the lichens (as far as this can be decided by a rough estimate). The difference as regards mass-occurrence (stated in weight) is not known (but at a rough estimate it would not seem to be great; the mass -occurrence is greatest perhaps on the Danish heaths). With respect to growth- forms the similiarity also appears to be rather great, but it will probably, on a closer investigation, be lessened by the fact that more crustaceous lichens will be found on the heaths of Iceland, than on those of Denmark. The systematic species of the two countries differ by no means slightly from each other. It may therefore be said generally, that the conception "heath," as we know it from Denmark, does not undergo any great funda- mental change through a closer investigation of the Icelandic heaths. After having thus dwelt upon the appearance of the lichen- vegetation, it now remains for us briefly to point out the conditions which the lichens find on the heath and which have a determining influence as regards whether they thrive or do not. The following are the most essential: (1) Nowhere on the heaths did I observe, that the chemical composition of the soil had a detrimental influence on the lichen- vegetation but in other localities, for instance near Solfataras, etc., the conditions were very unfavourable to them. (2) Thermal conditions and water contents are so closely con- nected with each other, that it is usually difficult to separate them. Damp, cold soil is generally unfavourable to man}" lichens (compare Bogs), whilst desiccation is not detrimental to them in a climate where the precipitation is as great as it is in Iceland. The greatest degree of moisture which permits the growth of heath-vegetation (i.e. F. o 100 chamaephytes) is however also favourable to lichens (mountain-heaths at higher altitudes). (3) Loose, drifting soil frequently bears heath-vegetation, when the soil does not drift very greatly. But such heaths are devoid of lichens. (4) Leal-fall, which covers the lichens, does not hamper them greatly on the heaths; luxuriant dwarf-birch growths and in some degree a lew other larger species may, however, by this means prevent the appearance of lichens. LICHENOLOGY OF ICELAND 217 (5) The snow-covering in some localities has a not unfavourable influence provided it disappears for a few weeks every summer with- out leaving too great masses of water behind it (in which case mosses and algae gain the upper hand). The heaths of mountain heights are sometimes rather rich in lichens. (6) Conditions concerning the nivean of the ground, appear to be of fairly great importance, inasmuch as knolly ground, in most cases, bears lichens on the sides of the knolls, whilst the horizontal surfaces of the knolls are covered with lichens in damp heaths only. The depressions between the knolls frequently bear mosses and no lichens at all or only a minute quantity. Here, it is most probably, the conditions of moisture that make themselves felt. (7) The plant -covering (the competitors) plays essentially the part of contending against the lichens by covering them with de- caying leaves (see above) or by overshadowing them. Both these drawbacks occur on Icelandic as well as on Danish heaths, where the higher plant-growth is more luxuriant. But experience shows that the growth and luxuriance of the chamrephytes themselves is not great enough on all heaths to exclude lichens. f. Coppices. These, the only phanerophytic birch-vegetation of Iceland, are, as elsewhere mentioned in this work (see vol. I, p. 312 et seq.), widely distributed over the whole of the island, but may, how- ever, possibly be absent from a narrow strip of North Iceland. They do not extend upwards on the mountains beyond a height of about 550 metres, and the majority of them are situated at lower levels. Everywhere the coppices consist, to a certain extent, of rather poorly developed individuals, the height of which ranges from that of a low- growing shrub to a height of several metres (8 9). (The most frequent height is 1 2 metres). The density of the tree-trunks varies considerably, which consequently results in a fairly varying ground-vegetation. The soil is often knolly clay, and rests on gravel or also on rock, but sometimes there is a stony bottom, and sometimes the bottom is boggy soil (Thoroddsen, p. 342). According to H. Jons- son the most common ground-vegetations are: heat her- moor (of Empetrum nig rum, Arctostaphylos iwa ursi and Vaccininm uliginosiim), grassland (of Agrostis uulgaris, Aira flexuosa, Anthoxanthum, Festuca rnbra), herb-flat (of Angelica siluestris, Spircea Ulmaria. etc.) and 218 OLAF GALL0K moss-vegetation (of Hylocomium proUjernin, H. trujuetrum, H. sffimrrosnm, H. parietinnm and Climacinm dendroides). In Halsskogur I noted a vegetation consisting of various grasses, of Arctostophylos, dwarf birches, Vacciniiun ulic/inosiim. Eqnisetuin, linbus saxatilis, Empetrum and a few other plants. The ground \vas in part covered with decaying birch-leaves, forming a layer of about 2 6 cm. in depth, and the trunks had an average height of about 3 metres. The ground there was quite devoid of lichens as were also the trunks. The information contained in the literature on the subject, as regards the ground-vegetation of coppices, is not very exhaustive, and does not give much information with regard to how far lichens occur or not. One must, however, expect that coppices, the floor of which is occupied by heath-vegetation, can also harbour lichens, but nothing concerning this is mentioned in the literature on the subject, and I myself have not seen any coppices with an actual ground-vegetation of heath. Nor is there any information to hand as to how far grassland, mat-herbage or moss-carpets, when occur- ring as ground-vegetation, shelter lichens. It is, however, certain that earth-lichens may occur here and there, but even in the most favourable cases, they are but few in number and physiognomic-ally little dominant. H. Jonsson mentions for instance "Cladonia-species" (which?) as occurring near Breidibolstadir (South Iceland) and says that they occur there "abundantly, but are far from playing so important a part and from being so widely distributed, as in South Greenland." I myself only once found a small tuft of Cladonia pityrea. I do not doubt that, on the whole, the floor of the coppices may be regarded as poor in, or devoid of, lichens and the reason for this is undoubtedly to be found as usual, in the want of light and in the leaf-fall. Nor does the ground-vegetation of willow-coppices appear to include lichens. The epiphytic flora will be mentioned elsewhere, so I shall not enter into the subject more fully here, \\here only the earth-lichens of the plant-associations are being discussed. LICHENOLOGY OF ICELAND 219 3. ROCK-LICHEN ASSOCIATION. By far the greater part of the rocky substratum of Iceland consists of basalt, but recent lava and liparite occur also, the latter, however, in a small quantity only. All these three kinds of rocks are fine-grained volcanic rocks. Considered from a chemical point of view, lipartite differs distinctly from the other two, in that it is of the same mineralogical composition as granite, and is conse- quently rich in silica. How the lichens penetrate into these substrata with their hyphse has not been investigated even in the case of a single species. The same applies also to the Icelandic tuff - - cemented volcanic ashes of a similar chemical composition as lava, but of quite dif- ferent physical qualities. We shall now consider more fully the individual substrata and their vegetation. a. Basalt. On this kind of rock there occur, as on many others, lichen- vegetations which vary greatly. They may be classified according to different principles exactly as is the case with vegetations on loose soil. I consider it best - - as in the case of earth-vegetations - to take the plants themselves as a guide in the classification, and shall therefore treat the associations in three main groups, viz. associations of crustaceous, foliaceous and fruticose lichens respec- tively; under the last group there are two essentially different sec- tions, viz. erect and pendulous lichens. With regard to these associations it may be said in general that: Crusta ceo us-lichen -associations grow T on rocks of all possible angles of declivity on horizontal surfaces, on vertical or sloping rock-faces, and on roofs of caves. Foliaceous lichens grow in a similar manner to crustaceous lichens on horizontal surfaces, on vertical or sloping rock-faces, and in caves. Erect fruticose lichens are found only on horizontal and on gently inclined surfaces, because they are as a rule very slightly attached to the substratum, in fact, they are generally attached to other plants which in their turn are anchored to the substratum, they are not themselves immediately attached to the rock-substratum. They are absent from vertical rock-faces and from the roofs of caves 220 OLAI- GAI.L0K Pendulous fruticose lichens can he found on rocks of all degrees of inclination: horizontal surfaces, vertical and sloping rock- faces, etc. The associations may be - - as in the case of the phanerogams divided into formations, facies or whatever we may choose to call them, and they may he named after the one or more species which dominate the community. In addition to the chemical and physical qualities of the rock and the degree of inclination of the substratum, there are other conditions which play a part as regards the physiognomy of the vegetation, primarily conditions pertaining to moisture, and the competitive relations between the species themselves. Thus the same vegetations are not found on rocks wetted with spray, on submerged rocks and on dry emergent rocks. The quality of the water also - - salt, fresh or distilled (rain) water - - plays an essential role here. Moreover, it is of no slight importance, whether the rocks are frequently manured by birds or whether this does not take place. We can, as already mentioned, divide the associations, which are produced by the action of each of these complexes of life-con- ditions, in very different ways: we may speak of "nitrophilous associations" (Sernander), of halophilous associations, associations of hollows, associations of horizontal surfaces, etc., according to our knowledge of the factors which determine the association. But this mode of naming them appears to me to be extremely unpractical, because we may very often be at a loss with regard to the group to which we are to refer the association in question. It is in reality not at all possible to draw a decided line between a nitrophilous and a non-nitrophilous association: all lichens are in fact nitro- philous to some degree. It is the same difficulty with which the ecologists have had to contend as regards the soil-associations, but in this department order is appearing owing to the fact that the association is not named after Factors as a rule imperfectly known - - which condition its well-being ("sand-vegetation," "rock-vegetation," "xerophilous cop- pice," etc.), but after the plants themselves (phanerophyte-vegetation, chamaephyte-vegetation, etc.). Whether one choose the one or the other mode of procedure is by no means a matter of indifference. The associations living in nature are naturally the same, whether we give them the one or LICHENOLOGY OF ICELAND 221 the other name, hut for the sake of synonymy it is necessary to have simple and easily definahle conceptions, and this is hest done by naming the association after the dominant plant-growth-form. With regard to lichens we will therefore employ as the prin- ciple of main division the grouping indicated above, vi/. that of crustaceous, foliaceous and fruticose lichens, and, as far as possible, follow them on each rock-substratum. The Crustaceous-lichen-association is widely distributed on all kinds of basalt. Several types (formations) may be distin- guished, e. g. mixed crustaceous-lichen-formations, Staurothele- formations. C/o/)/aca-formations and Verrucaria-formations. Mixed crustaceous-lichen- formations are widely distributed especially on the almost vertical faces of basalt rocks along the fjords. The plant-density is often rather slight, in that the individuals are not in contact with each other, i. e. they leave the rock-surface visible between them. In such places, therefore, there is no actual competition between the species, and the community is consequently analogous to the desert-vegetation of loose soil. In other places the plants may be closely in contact with each other, and struggle for space. In this case competition arises, where sometimes the one and sometimes the other plant predominates, but all the circumstances concerning this interesting struggle have not been investigated and are not known. Many interesting observations could undoubtedly be made as regards the frequency-number and mass-occurrence of the single species under different conditions, but all this requires both a long sojourn and also patient investigations on the spot. I presume, that among other things, we should thereby acquire a closer knowledge of the life-necessities of each species, and that we should be able to sub-divide the "mixed crustaceous-lichen-associalions" into per- haps as many formations as the number of the systematic species. But this the future must decide. To this association almost all the crustaceous lichens of Iceland must undoubtedly be referred, i. e. somewhat above 100 species. There are, however, some which occur repeatedly and which ought to be enumerated as characteristic of the association, viz. Lecanora cinerea. Lecanora intricata. pallescens. frustulosa. atra. sordida v. glaucoma. TJl' OLAF GALL0E Lecidea pantlicrina. Lecidea data. cyanea. Bhizocarpon geograpbicum. erratica. ^eminatum. speirea. Caloplaca vitellina. lapicida. Physcia aipolia. elaeochroma. Occasionally there also occur mixed with the above: Racodium rupestre, Poly blast ia hyperborea, Acorospora Heppii, A. fnscata, Catil- laria alhallina and a few foliaceous lichens fParmelia lanata. Gym- phora cylindrica and G. erosa). This association grows from the coast where it begins a short distance above the Verrucaria-loell - - to far up the mountains, where it stops at the snow-line. As regards its luxuriancy at various heights above sea-level, very little is known, but it appears to be least developed at great altitudes. I myself had a distinct impres- sion of this for instance from my observations on the mountain Sulur near Eyiafi6r5ur and the mountains near Husavik (on the mf v v \ north coast), and H. Jons son states the same as regards the con- ditions on Snaefellsnses ; he writes: "The same is the case with the crustaceous lichens as with the phanerogams; they occurred ex- tremely sparsely on the stones in the upper part of the rocky flat." The association is quite absent from the pebbles on the shore: it cannot endure inundation by salt water. The Staurothele-asso elation occurs almost exclusively by waterfalls, where it forms black crusts on the rocks in all places where the spray from the falling water reaches. It is extremely characteristic of all such localities. Mixed among the slender, black lhalli of Staurothele occur crust-like thalli of various Cyanophycece, so that it is often difficult to decide which of them is the more abundant. I have never found any other species of lichen directly connected with this association, which therefore contains only the one species Slaurothele clopima. The Caloplaca-association (Placodium stramineum, P. alpho- placum and Caloplaca innronim), which on Bornholm (Denmark) is so common on the shore above the Verrncaria-belt, is very little developed in Iceland. I found only slight indications of it in SeyiTis- IjoiAiu. Helgi .lonsson records it from West Iceland. The Verrucaria-association, formed by V. nmnra and an inconsiderable quantity of Lichina con finis, which is well-known from Bornholm and from all the other rocky coasts of the North, is ;i|so found in Iceland, where it borders the sea-shore from high- LICHENOLOGY OF ICELAND 228 water level as far upwards as the spray of the waves reaches. I have seen it developed very distinctly for instance on the sides of SeyQis- fjorSur, Rey5arfj6r5ur, Eyjafjor5ur and in several other places. Its natural history is in all respects a repetition of what we know from Denmark, Finland, etc. Therefore, there is no special reason to dwell upon it more fully here. Foliaceous-lichen-associations are found here and there, fairly well-developed, especially in the low land, where they fre- quently consist of Parmelia saxatilis, P. lanata, P. stygia or of species of Gyrophora (G. cylindrica, arctica, erosa). Sometimes the one, sometimes the other species predominates, whereby several forma- tions may be distinguished ("Parme//a-formation," "Gyrophora-forma- tion," etc.). As far as my observations go these communities are most luxuriantly developed in places where it is light and damp. For instance, they are found well-developed by the waterfalls at the head of Sey5isfj6rdur and by Dettifoss (North Iceland). The density of the plants is as a rule high and consequently the competition is keen, but regarding this point no detailed in- vestigations have been made. The crustaceous lichens are however mercilessly exterminated when Parmelia saxatilis puts in its ap- pearance; in many places this process of extermination may be observed in various stages. It is more rare for the Gyrophora spp. to dominate so de- cidedly; I did not see them as pure growths, as they may be found in Arctic countries. The Fruticose-lichen-association. Helgi Jonsson re- cords that Ramalina cnspidata often occurs abundantly on the rocks of South-west Iceland. He does not, however, state more explicitely whether it actually forms carpets. I myself never saw it occur in such abundance as to make it justifiable to speak of Ramalina- carpets, like those found on the shores of Bornholm. Nor did I come across such a feature on the coastal rocks of Iceland. Usnea melaxantha may sometimes be found in tolerable abun- dance near the snow-line on mountain heights, but I did not see this species either actually form carpets. Therefore it appears that Iceland has no continuous carpets of pendulous fruticose lichens which are attached to the rock- substratum itself like those we have in Denmark. Erect fruticose lichens (Alectoria, Stereocaulon, Cladonia, Cetraria .acnleata, etc.) are frequently found covering the rock-substratum at J'J 1 OLA I C.ALL0K almost all altitudes. But it must be remembered that all the lichens belonging to this group, are more or less dependent upon the pre- sence of other plants, for as I have fully explained in my "Danske Licheners 0kologi" they always follow an initial vege- tation of other lichens (crustaceous or foliaceous lichens) or of mosses and live so actually on the soil formed by them that they are not even attached to the rock-substratum, but on the contrary, in some cases die away at the base. This circumstance has also been con- sidered more fully in the present treatise under the heading "Earth- lichens" and will not be discussed further here. An exception to this rule is formed, it appears, by Stereocaulon (lenmiatnm, which at least appears to be able to live upon the rock itsell. 1 have not found it, however, upon basalt, but in great abundance upon recent lava, and shall treat of it under the heading "Lava." b. Lava. The post-glacial lava is black, with many small cavities and vesicles, and sometimes of an appearance similar to cokes. When it gradually becomes covered with vegetation, this usually consists of Grzmmia-carpets, which again can develop into heaths, etc. But those areas which do not immediately become moss-covered, fre- quently become first lichen-covered. The lichens may occur on the rock-substratum itself, at first crustaceous lichens, then foliaceous and fruticose lichens. The latter are, however, probably most fre- quent in places where moss had first been growing. I have not had the opportunity of seeing lava at all altitudes, and therefore I am not prepared to say how far it supports Verrn- c) and Iceland 59 (about 15 %>, inasmuch as Iceland's 285 systematic species constitute 337 biological forms, as several of the species occur sometimes as earth- and sometimes as rock-lichens, etc.). Now the areas which have here been compared with one another, are far from being all equally large and therefore do not give any figures, which are useful for purposes of direct comparison. But, at any rate, they give an indication of the fact that bark-lichens are com- paratively more numerous in countries rich in trees than in Iceland ; and they give the very important-information that Iceland, although it is much larger than Denmark, has only 59 species, whilst Den- mark has 165! Whether this circumstance is solely due to want of necessary tree-substratum is not easy to decide. For instance, whether the bark-lichens of Denmark would be able to thrive in Iceland, if, by way of experiment, we removed them thither, together with the stems upon which they occurred, or whether the climate alone would kill them, we do not know. But that the paucity of species is due to the climate - - directly or indirectly - is evident enough. Epiphyllous lichens. These occur, as is well-known, on ever- green leaves only. 24 species are known to occur in tropical Africa and 3 in Italy. From the climate-belts north of Italy they are prac- tically absent, and in Iceland, with its deciduous birches and wil- lows, they are totally wanting. The same consideration which applies to the bark-lichens may be extended to the epiphyllous lichens, viz., that the climate is, directly or indirectly, a hindrance to their growth in Iceland. Earth- lichens. We must expect a priori, that regions with a luxuriant vegetation of phanerogams and other good-sized plants are not favourable to earth-lichens. From the whole of that immense, tropical Africa (outside its alpine regions) only some 50 lichens are known! (about 5 6 %), from Italy 275 (about 17 /o), from Denmark 86 (about 20 %) and from Iceland 121 (about 36 %>). As may be seen, the percentage of the earth-lichens becomes greater and greater, the farther we proceed northwards to the cold regions. This is without doubt correlated with the fact, that the number of the com- petitors of the lichens decreases towards the north, the ground be- coming more destitute of other plant-growth. 240 OLAF (1AI.I.0K But the absolute number itself is greater for Iceland than for Denmark! Does this imply that the climate up there in the north is more favourable to lichens than down here in Denmark? Does not this contradict our general assumption, that lichens are more abundant in temperate countries than in Iceland? Anything of this kind cannot be deduced from the aforesaid fact. Considering the particularly favourable conditions which Iceland can offer the earth- lichens as regards competition, the number 121 in proportion to the 104000 square km. of country is very modest compared with Den- mark's 86 on 38000 square km. Still more interesting conditions become apparent when we re- gard the sub-divisions of the earth-lichens: the crustaceous, foliaceous and fruticose lichens. It is then seen that Denmark and Iceland have the following earth-lichens: Crustaceous Foliaceous Fruticose Denmark .... . 34 21 31 Iceland 67 27 27 These figures are most peculiar, inasmuch as they show that Iceland's predominance as regards the number of earth-lichens, is due to a greater number of crustaceous lichens, inasmuch as both countries have about the same number of foliaceous and frulicose lichens, taken collectively, whilst Iceland has very nearly twice as many crustaceous lichens as Denmark. Remembering, that this growth-form in particular, in order to be able to live at all, de- mands either a very moderate competition, or none whatever, on the part of other plants, it is easily to be understood, that an Arctic country in particular, with a slightly developed phanerogamic vege- tation, offers the crustaceous lichens the most favourable conditions possible, as regards competition. In reality there is so much un- occupied ground, free from other plants, that we might expect a much greater number, offering an analogy with the fact, that much tree- vegetation (for instance in the Tropics, in Italy, etc.) serves greatly to increase the number of species of tree-lichens. When in spile of the very slight competition, the number of earth-lichens is so limited, this can only be regarded as a direct result of the climate. LICHENOLOGY OF ICELAND 241 Rock-lichens. With regard to these it can be stated that tropical Africa has 182 species (24 %), Italy 729 (46 %), Denmark 169 (3940 %) and Iceland 157 (47 %>). The figures indicate that the sub-tropics are rich, and the purely tropical regions poor, in species; whilst the temperate and Arctic regions are less rich in species than are the sub-tropics. On comparing more particularly Denmark with Iceland, we find that the number of species is greatest in Denmark, although Iceland is much larger in area. Remembering, moreover, that Iceland has bare rock-substrata, the superficial extent of which is so great that in Denmark we can form no conception of it, whilst our Danish species are limited to the very modest granite-surfaces on Bornholm, and to the loose stones found scattered about in fields and in fences, the small number connected with Iceland appears extremely eluci- datory. It is impossible to explain this as anything else than a direct result of the climate, because Iceland has so many kinds of rock-substrata, that there would be plenty for the lichens to choose among, if the climate had otherwise been favourable to them. We can consequently briefly sum up the above in the following few sentences: (1) Iceland (as also the Arctic countries) has on the whole a lichen-vegetation poor in species in proportion to its area, poorer than have the temperate and sub-tropical countries. (2) The Bark-lichens meet with the most favourable condi- tions in the tropics - - that is to say, they are rich in species there in the Sub-tropics and in the Temperate regions they are poorer, whilst in the Arctic countries and in Iceland they are poorest of all; this should probably be correlated w r ith the abundance of sub- strata present. (3) The Epiphyllous lichens find the most favourable con- ditions in the Tropics, less favourable in the Sub-tropics, and least favourable of all in the Temperate regions; in the Arctic countries and in Iceland they are entirely wanting. (4) The Earth-lichens meet with very unfavourable conditions in the Tropics, better in the Sub-tropics, better still (probably) in the Temperate regions, and best of all in the Arctic regions as regards conditions concerning competition. The climate, on the other hand, appears to be directly unfavourable to them in the Arctic regions and in Iceland. (5) The Rock- lichens meet with very unfavourable conditions The Botany of Iceland. Vol. II. 16 242 OLAl C.ALL0E in the Tropics, better in the Sub-tropics, better still in the Temperate countries, and best of all in the Arctic countries and in Iceland as regards conditions concerning competition. The climate, on the other hand, appears to be directly unfavourable to them in the Arctic regions and in Iceland. This is best shown in a Table: Bark-lichens Earth-lichens Rock-lichens Tropical Africa 498 (65 %>) 24 (3.2 %) 45 (5.8 %>) 182 (24 %>) Italy 508 (32 /o) 3 (0.2 %>) 275 (17 %>) 729 (46 %>) Denmark 165 (39 %>) 86 (20 %) 169 (39 % Iceland | 59 (15 % 121 (36 %>) 157 (47 %> These figures have been commented upon more fully in the above, both the actual figures and the percentages. But the other side of the matter still remains to be discussed, viz., the valuation of the wealth of the various regions as regards the mass-development, as far as this is manifested by frequency numbers and masses (given in weight per unit of area). Hitherto we have been exclusively dependent upon a superficial valuation of this, and we are as vet hardly bevond the very rudiments as *//*. fc regards this point, but it need not continue to be so in the future. I shall record here the little that is known and may be discerned, but, firstly I shall dwell a little on the precautionary measures which must necessarily be taken in order to be able to judge some- what correctly. The cause which chiefly leads us to judge erroneously, is the fact, that we are involuntarily deceived by the sixe of the phanero- gams compared with the lichens. Thus, we may very easily be struck by the abundance of lichens on mountain heights, in places where phanerogams are either totally or almost wanting, and on the other hand, underrate the abundance of lichens where the larger phanerogams are more numerous. This is in itself so common and significant a source of delusion when forming an estimate of the abundance of lichens, that as a rule we must be very cautious about relying on the results which the botanist in question puts forward, if we do not know beforehand his conception of this circumstance. But even if the botanist happens to judge quite correctly, yet he LICHENOLOGY OF ICELAND 243 has no other descriptive means with which to express his judg- ment than the terms "abundant," "less abundant," etc., merely relative expressions, which have no relation to any fixed and in- variable unit. It must therefore be absolutely recommended, in future, to de- termine the abundance of lichens in a country, a plant-association, a zone, etc., by still two other means, viz., frequency-number and mass-occurrence (in weight per unit of area) - in addition to its number of species. In the present treatise I have as regards some of the Icelandic associations as far as travelling-conditions permitted given some frequency-numbers, which may be obtained, for instance by demarcating small sample-areas (1 or 2 square decimetres each) with equally large, intermediate spaces between them in some places it is practicable to employ the smaller unit, whilst in other places the larger unit is preferable - and by noting whether they contain lichens. This method, as already mentioned, is RaunkiaBr's for phanerogams, and is also very good for lichenological purposes. In that way it is possible to determine almost all possible frequency- numbers in detail, to investigate for instance the frequency-number for crustaceous-lichens only, foliaceous-lichens only, etc., or the frequency-number for lichens taken collectively. If it be a question of wishing to know, for instance, how frequently lichens, as com- pared with phanerogams, occur in the sample-areas one can just take, say 100 200 or 1000 sample-areas, according to what may be considered necessary in order to obtain a reliable impression of the conditions, and note down in which areas lichens occur and in which phanerogams (mosses, alga?, etc.). If lichens occur in all the samples, then the frequency-number of the lichens is F /o 100 (F % stands for the frequency-percentage); if they occur only in 50 out of 100 sample-areas, then the frequency-number is F /o 50, etc. All this has been treated of above to some extent, but here it is explained more fully. - - In the case of phanerogams, mosses, etc. exactly the same method is employed. If one should wish to determine how frequently crustaceous, foliaceous and fruticose lichens occur among themselves, one must note down, with regard to each of these little sample-areas, which of these growth-forms occur in it. For instance, in a series of samples, crustaceous lichens may be found in 50, fruticose lichens in 100, and foliaceous lichens in 20 sample-areas. The frequency - 16* 244 01 AF C.ALL0E number is then F % 50, F /o 100 and F % 20 respectively, all of which has already been known and employed for several years in ecology, with regard to phanerogams. This frequency-number serves to indicate how equally the lichens are distributed in an association or similar limited area. This has the great advantage, that even non-specialists, who have a general botanical training, can note down various facts with regard to the distribution of special groups of plants (lichens, earth-alga;, mosses, etc.) in the associations, without knowing the name of a single species found. A specialist, when he has time at his disposal, will be able to go more into details, and even determine the distribution of a single species within a certain area. The determination of the mass-occurrence of lichens has never yet been undertaken; it has been mentioned under the treat- ment of the heath-lichens. For this determination it is necessary to reap everything that grows on each sample-area, and weigh it By this means one obtains figures, which are directly useful for purposes of comparison, as regards the relative extent of mass- occurrence of the plant-association in question. This method is useless as regards the crustaceous lichens, but in their case it is possible to state, with some certainty, the size of the area covered by them. If we are to compare the abundance of the lichens of the various countries, according to the methods which have been briefly treated here, and, by means of these methods, try for instance to answer the general question : "Where are the lichens to be found in greatest abundance, in Iceland or in Denmark?" This question must be further detailed, in order to be answered, and cannot, upon the whole, be answered as yet. The Icelandic heaths can be compared with the Danish, the Icelandic grasslands with those of Denmark, etc., as has been done above, by way of experiment, in the special sections, with regard to frequency-number and mass- occurrence (in weight per unit of area). But a thorough comparison cannot yet be made, as it requires many more investigations in the field, than have hitherto been undertaken. It is, however, my impression, as it has been the impres- sion of other botanists, already in former times, that as regards fre- quency number and abundance the Arctic regions and Iceland appear to be richer than other regions, no doubt chiefly on account of the LICHENOLOGY OF ICELAND 245 slight competition to which the lichens are subjected. It must, however, be remembered that the cold mountain heights in Iceland appear to be less rich in lichens, than are the more low-lying parts, and are remarkably poor when the fact is considered that the com- petition on the part of other plants is only slight, or altogether wanting; so that one is led to the conclusion that the climate, as such, is not favourable. BIBLIOGRAPHY. Babington, C. C., 1871: A Revision of the Flora of Iceland (The Journal of the Linnean Society, vol. XI, London). Deichmann Branth, 1903: Lichenes Islandi;e Botan. Tidsskrift, Bd. 25, Kjeben- havn). Ferdinandsen, C., 1918: Undersegelser over danske Ukrudsformationer. (Diss. Kjobenhavn). Gallee, O., 1908: Danske Likeners Okologi Botan. Tidsskr.. Bd. 28, Kjebenhavn). , 1913: Forberedende Undersogelser til en almindelig Likenekologi (Dansk Botan. Arkiv, Bd. I, No. 3, Kjebenhavn). Gelert og Ostenfeld, 1898: Nogle Bidrag til Islands Flora (Botan. Tidssk., Bd. XVI, Kjobenhavn). Gronlund, Chr., 187071: Bidrag til Oplysning om Islands Flora iBotan. Tidskr., Bd. 4 . , 1873: Bidrag til Oplysning om Islands Flora (Botan. Tidsskr., Bd. 7). , 1877: Islandske Naturforhold med saerligt Hensyn til Mosvsextens Betydning for Landskabet Tidsskr. for popula?re Fremstillinger af Naturvidenskaben, 5. Baekke IV. Kjebenhavn). , 1881: Islands Flora ( Kjobenhavn). . 1884: Karnkteristik af Planteva?xten paa Island sammenlignet med Floraen i flere andre Lande (Den Naturhist. For. Festskrift, No. 1. Kjobenhavn). , 1885: Afsluttende Bidrag til Oplysning om Islands Flora (Musci, Hepaticse, Lichenes). - - (Botan. Tidsskr., XIV, Kjebenhavn). , 1895: Tillseg til Islands Kryptogamer (Botan. Tidsskr., Bd. XX, Kjebenhavn). Hayren, E., 1914: Ueber die Landvegetation u. Flora der Meeresfelsen von Tviirminne. (Acta Soc. pro Flor. et Fauna, Fenn.). Hesselbo, Aug., 1918: The Bryophyta of Iceland (The Botany of Iceland, Part II. Copenhagen and London). J6nsson, Helgi, 1895. Studier over 0st-Islands Vegetation (^Botan. Tidsskr., Bd. XX). , 1899: Floraen paa Snaefellsnses og Omegn Botan. Tidsskr., XXII). , 1900: Vegetationen paa Sniefellsna?s (Videnskab. Meddelelser fra den Natur- hist. Forening. i Kjebenhavn). , 1905: Vegetationen i Sydisland (Botan. Tidsskr., XXVII). Lauder Lindsay. 1861: Flora of Iceland New Philosophical Journal, New series, Edinburgh). Mentz, A., 1913: Studier over danske Mosers recente Vegetation v Kjobenhavn og Christiania. Bot. Tidsskr. XXXIV Ostenfeld. C. H., 1899: Skildringer af Vegetationen paa Island (Botan. Tidsskr., Bd. XXII . Petersen, H. E.. 1917: Maglemose i Grib Skov. (Botan. Tidsskr., Bd. 36). BIBLIOGRAPHY 247 Raunkiaer, C., 1909: Formationsundersegelse og Formationsstatistik (Botan. Tidsskr., Bd. 30). , 1912: Measuring Apparatus for Statistical Investigations of Plant Formations (Botan. Tidsskr., Bd. 33). , 1916: Om Valensmetoden (Botan. Tidsskr., Bd. 34). , 1917: Becherches statistiques sur les formations vegetales (I)et Kgl. Danske Vid. Selsk. Biolog., Meddelelser I). Rostrup, E., 1888: Bidrag til Islands Flora (Botan. Tidsskr., XVI). Stefansson, St., 1890: Fra Islands Vsextrige, I III (Vid. Medd. fra Nat. For. i Kjobenhavn). , 1896: Bemaerkninger til Chr Gronlunds Tillseg til Islands Kryptogamflora, etc. (Botan. Tidsskr., Bd. XX). , 1901: Flora Islands. (Kobenhavn). Stromfelt, H. F. G., 1884: Islands karlvaxter (Ofversigt af Kgl. Vetensk. Akad. Forhandlingar, Stockholm). Thoroddsen, Th., 1914: An Account of the Physical Geography of Iceland, etc. (The Botany of Iceland, Part I, 2, Copenhagen and London). Warming, E., 1895: Plantesamfund (Kjobenhavn). , 1909: Oecology of Plants (Oxford). CONTENTS. Page Introduction 103 I The Lichen Flora of Iceland 106 II The Means of Propagation and Dispersal of the Iceland Lichens 130 III The Biology of the Lichens of Iceland 137 1 . Bark Lichens 137 2. Epiphj'llous Lichens 142 3. Karth Lichens 142 4. Hock Lichens 156 5. Synopsis of the chief Biological Conditions of the Lichens of Iceland 164 IV The Classification of the Lichens into Associations 172 1. Bark-Lichen Association 172 2. The Earth-lichen Associations 174 a. The Deserts 182 h. Lichen-heaths 187 c. Moss-vegetations 187 d. The Grass Vegetation 191 e. Heaths 197 ^H f. Coppices 217 3. Rock-lichen Association 219 a. Basalt 219 h. Lava 224 c. Tuff 227 d. Liparite 22S V The Vertical Distribution of the Lichens 230 VI The Abundance of Lichens in Iceland 234 Bibliography 246