32 F. E. FRITSCH. 



(Menegh.) Gom., but apart from other differences, the trichomes are more nioniliform 

 than they are in that species. The longer cells, granulated dissepiments and more 

 markedly nioniliform character distinguish P. frignlum from /'. ylwiale W. and 

 G. S. West (op. cit., p. 291, 292). 



42. PHORMIDIUM ANGUSTISSIMUM. 



Phormidium angmtissimum \V. and G. S. West, " Welwitscli's African Freshwater Algae," Journ. Bot., 

 1897, pp. 298-299. 



Nab. Freshwater pond in eskers upon ice, half way between Black and Brown 

 Islands, January 3rd, 1903; freshwater pond in ice off Black Island, McMurdo 

 Strait, December 31st, 1902. 



In the material from the first habitat the septa were very indistinct and 

 constriction was scarcely obvious. In this latter respect the specimens were more like 

 P. treleasl Gom., which G. S. West (Algae from hot springs, Journ. Bot., 1902, p. 245) 

 has suggested may be identical with P. angustissimwn. In some cases the trichomes 

 tapered a little at the apex. The material from the second habitat was quite typical. 



43. PHORMIDIUM ANTARCTICUM. 

 (PI. I., tigs. 71-73.) 



Phormidium anfarcticum W. and G. S. West, Rep. Brit. Antarct. Exped., vol. i. (1011), p. 292, PL XXV., 

 figs. 75A-75G. 



Forma trichomatibus modo laxissime spiraliter contortis vel non spiraliter. 



Hob. Pond some distance behind hut, Cape Adare, January 9th, 1902. 



The material of this species occurred intermingled with CUamydomonds 

 tsubcaudata, C. intermedia, etc., i.e. the consorts were in part the same, as in the 

 material examined by Messrs. West. The filaments agreed in all respects with those 

 described and figured by the latter authorities, except that they did not show the 

 marked spiral character evident in Messrs. West's figures. They were sometimes 

 formed into a very lax and irregular spiral, but more commonly a spiral character 

 was not obvious at all, the filaments being almost straight or curved or looped in 

 various ways. 



The diffluent sheaths of the filaments were rarely visible, but were often indirectly 

 rendered obvious by the marked adhesion of foreign matter (in the shape of minute 

 particles) to the surface of the filaments. The transverse walls were very indistinct in 

 unstained material, but after staining with methylene blue they appeared as rather 

 thick transverse bars. 



The advisability of referring this form to the genus Pkonnidium may be 

 questioned. Except for the diffluent character of the sheaths, it is a Lyngbya, and it 

 might prove better to confine the limits of the former genus to such forms as consist 

 of sheets of agglutinated filaments. 



