THE FRESH-WATER CYANOPHYCEÆ OF ICELAND 275 



In the Icelandic sample it grows together with Oscillatoria liinosa among 

 Ulothrix and Zygnema. 



Oscillatoria tenuis Ag. 



C.omunt, Moiiogr. II p. 220, pi. VII, figs. 2—3. 



N. Icel. Stora Gja on niud ^^/^ 1914. 



Area: Ubiciuist. Fr. Josephs Land, Lappland, Beeren Eiland, Green- 

 land, Færoes. 



O. tennis has a world-wide distribution and occurs under the most 

 varying extcrnal conditions. Besides appearing in stagnant as well as 

 running fresh water it has also been found in brackish water and hot 

 springs (40 '^ C. Borge 1906 p. 10). It often grows on moist earth, e. g. 

 at the Icelandic locality this being a lava creek at the bottom of which 

 a hot spring flows out. 



According to Maertens (1914) it should need. a great quantity of ni- 

 trogen, and Kolkwitz et Marsson (1908 p. 51 1) class it as a-mesosaprobe. 



Oscillatoria amphibia Ag.? 



Gomont, Monogr. II p. 221, pi. VII, ligs. 4—5. 



N. W. Icel. Botn in GeirljjofsfjorSur, lake at 200 m., temp. 8 ^ ^6/^ 

 1915. (H. J.)! 



Area: Ubiquist, Spitzbergen, Beeren Eiland, Greenland. 



The determination of this species cannot be said to be absolutely 

 certain as I have not observed any curved apex; on the other band the 

 dimensions are in accordance. 



O. amphibia does not belie its name, being found in fresh. brackish 

 (e. g. Schultz 1914 p. 23, West 1909 p. 243) as well as in thermal-water 

 (e. g. Fritsch 1914 p. 52, Borge 1906 p. 10) and showing thereb}' great 

 powers of adaptation to the physical and chemical qualities of the water. 

 It has, in faet, also been found in the coldest as well as the warmest 

 regions of the earth. 



Oscillatoria brevis Kiitz. 



Gomont, Monogr. II p. 229, pi. VII, figs. 14—15. 



S. Icel. Laugarne, Reykjavik, 40 <* C. Vio 1897 (H. J.)! 

 Area: All continents, Antarctic, Greenland. 



The specimen in question was first determined by J. Schmidt and 

 I have later revised the determination. 



O. brevis possesses great power of adaptation. It is found in fresh 

 as well as salt water (var. neapolilana); furlhermore it appears as aéro- 

 philous alga on damp walls (Kaiser 1914 p. 146). Bohlin (1901 p. 73) 

 and Puymaly (1921 j). 190) have previously found it in hot springs. By 

 culture experiments Maertens (1914) arrived at the conclusion that it 

 needed considerable quantities of nitrogen in order to thrive well. This 

 is in accordance with Kolkwitz and Marsson (1908 p. 511) who place 

 it in their ecological sj'stem as a-mesosaprobe. 



