FRESHWATER ALG^E 291 



Genus PHORMIDIUM Kiitz. 



55 Phormidium autumnale (Ag.) Gomont 



I.e. 1892, p. 187, t. 5, f. 23, 24; Johs. Schmidt, " Danmarks blaagroenne Alger," 

 Bot. TidssJcrift, Bd. 22, Heft 3, 1899, p. 348. Ph. uncinatum (Ag.) Gomont, l.c. p. 204, 

 t. 5, f. 21, 23. 



Crass, trick. 4.6-7 M. (PI. XXV, Figs. 77-85) 



Hob. Pony Lake. Coast Lake. Ponds on Mt.-Erebus. 



This Alga appears to be frequent in the Antarctic regions, and was recorded from 

 the Falkland Islands by Hooker and Harvey as long ago as 1847. It occurred in great 

 abundance in Pony Lake, and the ends of the trichomes were furnished with precisely 

 similar small clusters of Bacteria as one so constantly observes in European specimens. 



It not only occurred in pure masses, but was frequent in the strata of other species 

 of Phormidium. 



As pointed out by Johs. Schmidt, there is no question of the identity of Ph. 

 autumnale and Ph. uncinatum. There are no characters by which it is possible to 

 discriminate between them. 



56 Phormidium retzii (Ag.) Gomont 



l.c. p. 195, t. 5, f. 6-9. 



Crass, trich. 6-6.5 /. 



Hob. Dried-up lake, Cape Royds, among Vlothrix cequalis Kiitz. 



57 Phormidium inundatum Kiitz. 



Spec. Alg. 1849, p. 251 ; Tab. Phycol. I, p. 32, t. 45, f. iii; Gomont, l.c. p. 192, 

 t. 4, f. 31, 32. 



Crass, trich. 3.5-4.1 /. 



Hob. Among Calothrix sp. in lake at Hut Point. In pond at Cape Barne, 

 abundant among Oscillatoria sancta. 



A slightly thicker form (crass, trich. 4.6-5 M), but well within the limits of size for 

 this species, also occurred in Blue Lake. 



58 Phormidium fragile (Menegh.) Gomont 



l.c. p. 183, t. 4, f. 13-15. 



Crass, trich. 1.2-1.6 M. 



Hob. Pony Lake, Green Lake, and Coast Lake. 



Forma tenuis. (PL XXV, Fig. 76) 



Crass, trich. 0.9-1 n. 



Hab. Coast Lake. 



59 Phormidium glaciale sp. n. (PI. XXV, Figs. 73-73d) 



Ph. strato valde expanso, laete aeruginoso vel aeruginoso-cceruleo, usque ad 2 mm. 

 crasso ; fills flexuosis densissime tortuoso-intricatis, vaginis in muco hyalino diffluen- 



