THE FRESHWATER CYANOPHYCEÆ OF ICELAND 279 



further statement as to whether the alga also actually grew in water of 

 this temperature. Howcver, in Tilden (1910 p. 97) \ve liave a deflnite 

 statement that it grew at 51 ^—5Q ^ C. 



Phormidium tenue (Mehegh.) Gom. 



Gomont, Monogr. II p. 169, pi. IV, flgs. 23-25. 



N. Icel. Reykhus, S. of Akureyri, hot spring 480-50*^ ^^/V 1914 (2 

 samples). Akureyri, hot spring ^^/e 1903 (O. P.,)! — N.W. Icel. Reykhohir, 

 margin of hot spring, 20*^ in the algal layer. ^/t 1919 (H. J.)! — ^Y. 

 Icel. Hveravellir, in spray of small geysir, temp. 85 '^ C. (West 1902 

 p. 245). Stora Kroppar, laug, temp. 26*^ ^/s 1914. — S. Icel. Reykir, at 

 margin of hot spring. The temp. of the spring 100—102". Stp.! 



Area: All continents, Antarctic, Fr. Joseph's Land, Spitzbergen, 

 Alaska. 



In none of the above-mentioned samples have I found a bent apex 

 corresponding to the one in Gomonf^s tig. 25. Neither have I succeeded 

 in discovering such an apex in the exsiccata ciled by Gomont, Rab. 

 Algen nr. 268 and 1730. P. tenue is dislinguished from P. laminosiim 

 chiefly by the constrictions between the cells and the absence of gra- 

 nules at the transverse walls. In Iceland it has only been found at the 

 hot springs, and with certainty in water of a temp. at 26 '^— 50 ^. Wests 

 statement that it occurs in a small geysir at a temp. of 85 *' C. must 

 be received with every possible reservation in that the author had not 

 collectcd the algae himself; they probably grew at the margin of the 

 spring where the temp. was considerably lower. 



For the rest the species has been found under highly varying con- 

 ditions, viz. in thermae, fresh water, brackish water, on earth; Miss 

 Bristol (1919) even found it in an old soil sample from 1868. This 

 sample contained comparatively much water, and she therefore considers 

 the species incapable of withstanding any longer period of drought. 

 Later the same author (Bristol 1920) has found that it is a very com- 

 mon occurrence in cultivated soil in England. 



'O* 



Phormidium subuliforme Gom. 



Gomont, Monogr. II p. 169, pi. IV, fig. 26. 



W. Icel. Hveravellir, temp. 55^ C. (West 1902 p. 245). 

 Area: St. Paul (the Pacific), Algiers, N. Am. (Nebraska). 



I have had no opportunity of observing this rare species. It has 

 only been found four times in all. 



Phormidium angustissimum W. et G. S. West. 

 Journ. of Bot. 1897 p. 298. 



G.S.West (1902 p. 245) mentions that he has found this species 

 in Iceland, viz. on the following localities: 



"Hveravellir, in hot spring, temp. 55 ^ G. Also in spray of a small 

 geysir, temp. of spra}' 85 ^ C. In the stream from the Great Geysir, 

 mean temp. aboul 40 "^ C." 



West makes the suggestion that this species is identical with P. 

 Treleasei Gom. Regarding this suggestion I cannot express any opinion 



