284 .ions. iu)Yi-: i'i.ti:hsi;\ 



Accordin^ to Gomont /' unciruilniu A^. (ioiu. is n species }4ro\vinj» 

 especially in wnler, stnf^nant as well as riiiiniii;^. win-icas /'. iniliiiniHilc 

 cliielly is foimd oii soil and most fre(|iientl\ iii the viciiiity ol' luiman 

 dwi'Ilinjis. Joiis. Schmidt 1. c maintains thai no valid morpholoj^ical 

 distin^iiishinj^ characters hctween the two species exist, and also Ihat 

 they cannot be se|)arated with regard to habitat. Ile thcrefore unites 

 them under P. (iiitiminalc. Neitber has G. Schmid 1917 p. 351, aecor- 

 dinj,' to my ojjinion. succeeded in discoverin^' aiiy valid dislinj^iiishinrt 

 characters bctween the two species. I tiiercfoie Ibllow .1. Schmidt, i)iit 

 I have. however, in the above mentioned list of localilics recorded where 

 I found pronounced u/j(//}a////??-f'orms. All my own collections originale 

 from earth, and among those pronounced P. iinriiuilniu was only present 

 in one sample, but besides I have found this form rather pronounced 

 in three samples colleeted by Helgi Jonsson and C. H. Ostenfeld. Whether 

 these samples originale from water cannot be seen from the labels, ex- 

 cept in the case of the sample from Laugarne at Reykjavik colleeted by 

 H. Jonsson "-'Vs 1897. On this is written : The heat at the surface 

 + 21^ C, at the bottom + 17*' C." I draw the conclusion that this 

 sample was colleeted in the stream near the hot springs. The two 

 samples colleeted by Ostenfeld are ])resumably the same which be refers 

 to (1.S99 |). 238 where he states thai P. iinciiuiliun was found at 3U "— 

 33^, P. aiitiimiuile at 21 ^ C. Judging by the text of the pa|)ei- the algæ 

 were colleeted on the warm earth surrounding the springs. Should this 

 be correct, it would mean that we also here have a conce|)tion which 

 is at direct variance with that of Gomont in that P. iiiuindtinu in this 

 case appeared on earth. 



All the remaining samples originale, as already mentioned. from 

 earth, viz. from the immediate vicinily of houses, from fowling cliffs and 

 from a small island in Myvatn frequented by numerous nalatorial hirds 

 depositing their excrements there. This verifies the general supposition 

 Ihat P. (tiiliimnale is a species which to a great extent recjuires an abun- 

 dance of nitrogenous nulrition in its substratum. Kolkwitz and Marsson 

 (1908 p. 511) consider it also as a-mesosaprob, and the same ajijjlies to 

 the uncinalum form. 



IV. Lyngbya C. Agardh. 



Lyngbya æstuarii Mertensi Liebm. 



Gomont, Monogr. 11 p. 127, pi. 111, figs. 1—2. 



N. W. Icel. DyrafjonVir. Moist piaces near the shore ^% 1895 (C. 

 H. O.)! — S. Icel. "Knararnes Vs 1905 ,H. J.)! 

 Area: All continents, Antarclic. 



This species is commonly mel with in salt or brackish water, but 

 at times it is found, however. in pure fresh water, e. g. in Switzerland 

 (Kurz 1913 p. 363j or in liiermæ, thereby showing great powers of 

 adaptation under varying conditions. Gomonl 1. c. has already drawn 

 attention to this faet. 



The two Icelandic localities mentioned above are bolh situated near 

 the sea, and the probabililies therefore aic Ihat the soil has been saline 

 in hotli |)laces. 



