THK FRESH-WATER CYANOPHYCEÆ OF ICELAND 283 



Phormidium ambiguum Gom. 



Gomont, Monogr. II p. 178, pi. V, fig. 10. Wittr. et Nordst. Alg. ex- 

 sicc. nr. 1 172. 



N. Icel. Reykhus south of Akureyri; in outlet from hot spring, 

 temp. 40° ^Vt 1914. Namuskar^, hot spring, temp. 45 *^ ^'V? 1914. 



Area: Eur., As., Afr., Am., Spitzbergen. 



The specimens from Reykhus had trichomes 8—9 /t in diameter, 

 i. 6. approaching var. major Lemm. (1910 p. 127). It proved very diffi- 

 cult to obtain a distinct colouration in blue of Ihe sheath with chlor- 

 zinc-iodine; but finally I succeeded. The cited sample (W. et Nrd., nr. 

 1172) behaved identically. In the sample from Namuskar6, on the other 

 hånd, the trichomes had the typical diameter, viz. about 6 fi. 



P. ambiguum has previously been found in hot springs, e. g. by Strom 

 (1921 p. 18) in a sample from Spitzbergen. Moreover the species has 

 been found in fresh water, brackish water and in a soil-sample (Esmarch 

 1914 p. 265). 



Phopmidium subfuscum Kiitz. 



Gomont, Monogr. II p. 182, pi. V, figs. 17—20. 



Vestmannaeyjar, Heimaey. On a rock beneath a fowling-cliff. "V« 1914. 

 Area: Eur., As., Afr., Am., Lappland. 



This species apparently deviates considerably in its distribution from 

 P. autumnale, to which it otherwise is closely related in as much as it 

 has neither been found in any antarctic nor in any true arctic area, 

 but only at the boundary of this. On Vestmannaej'jar it grew in Com- 

 pany with P. autumnale, but is otherwise supposed to need less organic 

 matter in the substratum than the latter (Kolkwitz und Marsson 1908 

 p. 512: /J-mesosaprob). It has generally been met with in water, run- 

 ning as well as stagnant, so that its occurrence on a fowling cliff is a 

 remarkable faet. 



Phormidium autumnale (Ag.) Johs. Schmidt emend. 



P. autumnale Gomont, Monogr. II p. 187, pi. V, figs. 23—24. P. un- 

 cinatum Gomont, Monogr. II p. 184, pi. V, figs. 21—22. Johs. Schmidt 

 1899 p. 348. Ostenfeld 1899 p. 238. 



E. Icel. Norc^fjoråur June 1894 (H. J.)! (var. uncinatum). Vattarnes 

 1^7 1898 (H. J.)! — N. Icel. Ulfsbær, soil at dunghill ^Vt 1914. Geitey in 

 Myvatn, soil beneath Archangelica highly manured by excrements of birds 

 ^Vt 1914 (2 samples). — W. Icel. Modruvellir in Kjos, on soil in front 

 of the house ^/s 1914. Grund in Skorradal, among stones in a wall 

 Vs 1914. — S. Icel. Karastaciir, on soil among stones in a wall ^V« 

 1914. Laugarvatn, on soil abounding in refuse in front of the house 

 ^Vs 1914. I>ingvellir, on soil on a path near the vicarage. ^^/s 1914. 

 Reykjavik. Laugarne (C. H. O.)! Ve 1896 and ^Vg 1895; ibid. (C. H. O.)! 

 ^/e 1896 (y ar. uncinatum); ibid. (H. J.)! ^i/g i897 {\ar. uncinatum). At 

 Laugarne, open place in grass moor ^/s 1914. — Vestmannaeyjar, Hei- 

 maey, fowling clifi" -Vs 1914 (3 samples). ? I^orisholmi '^e 1897 (H. J.)! 



Area: Ubiquist, Lappland, Spitzbergen, Færoes, Greenland, Arctic N.Am. 



19* 



