238 Minnesota Algae 



ing together laterally, branched, consisting of a single row of cells, rarely 

 of twQ rows, enclosed within a sheath; branches erect, usually about the 

 same thickness as the creeping primary filament, commonly unilateral, long, 

 flexuous, very slightly tapering; sheaths continuous, strong, of uniform 

 thickness; sheaths of the branches thinner than those of primary filaments, 

 usually colorless; heterocysts intercalary; wall of gonidium thick, yellowish 

 brown. 



I Plants living in fresh water. 



1 Filaments decumbent, branched on all sides; branches 6-8 mic. in 



diameter; cells elliptical depressed H. ilexuosus 



2 Plant mass caespitose, orange brown; primary filaments 11.5-12.5 mic. 



in diameter; trichomes 7.5-8 mic. in diameter H. aureus 



3 Plant mass floccose, caespitose, dull blue-green; primary filaments 



21-24 mic. in diameter H. fontinalis 



II Plants living in hot water 



1 Plant mass cushion-like, irregular or expanded, blue-green; primary 



filaments 3-6 mic. in diameter H. laminosus 



2 Plant mass widely expanded, bright blue-green; trichomes 3-1 1 mic. 



in diameter H. major 



III Plants living on bark of trees 



1 Plant mass caespitose, small, blue-green; filaments 4-7 mic. in diame- 



ter H. intricatus 



2 Filaments 7-10 mic. in diameter; trichomes 7-9.S mic. in diameter 



H. arboreus 



439. Hapalosiphon flexuosus Borzi. Alghe d'Acqua Dolce della Papuasia. 



La Nuova Notarisia. 43. 1892. De Toni. Syll. Algar. 5: 570. 1907. 



West and West. On some Freshwater Algae from the West Indies. 

 Tourn. Linn. Soc. Bot. 30: 272. 1895. 



Filaments decumbent, branched on all sides, consisting of a single row 

 of cells; branches 6-8 mic. in diameter, about equally thick in all parts, 

 flexuously interwoven; sheaths thin, smooth; cells elliptical depressed; 

 heterocysts similar to vegetative cells in form and size. 



West Indies. In stream. Grande Soufriere, Dominica. November, De- 

 cember 1892. (Elliott). 



440. Hapalosiphon aureus West and West. Welwitsch's African Fresh- 



water Algae. Journ. of Bot. 241. 1897. De Toni. Syll. Algar. 5: 571. 

 1907. 



West. West Indian Freshwater Algae. Journ. of Bot. 42: 291. 1904. 



Plant mass caespitose, densely interwoven, orange brown, growing 

 among other algae; primary filaments 11. 5-12.5 mic. in diameter, tortuous 

 and interwoven, formed of a single series of cells; sheaths firm, tenacious, 

 thick, orange brown, transparent, finally becoming punctulate; trichomes 

 7.5-8 mic. in diameter; cells somewhat quadrate or spherical, shorter than 

 the diameter and somewhat ellipsoid, or oblong and seven or eight times 

 as long as broad; branches 6.5-9.5 mic. in diameter, frequently unilateral, 



