SPECIES OF ALG^E. 63 



b. Floating, dichotomously branched, apices slightly bent; diameter 

 15-20/1 lacucola, 239 



b. Attached (V). 



c. Ends rounded, obtuse, fibrous with age, bluish . crustaceum, 239 



c. Ends tapering, or hair-pointed (d). 



d. Forming a stratum (f). 

 d. Forming tufts (g). 



f. Branches tapering to a fine hair-point .... Horsfordii, 239 



f. " cuspidate at apex or obtuse .... Orsiniana, 236 



g. Tufts small, wavering; filaments somewhat curved, clustered, ra- 



diating; sheath up to 3o//, wide radiosa, 239 



g. Tufts bright bluish, sometimes brown; sheath widens with age, 



Brebissonii, 238 



82. MASTIGONEMA. 



Filaments rounded or truncate at apex (a). 



" tapering to a hair-point (b). 



a. Sheath thick, apex truncate, open; diam. 8/1 . . . fertile, 244 



a. " in young plants ending in a seta, becoming open and trun- 



cate; diam i2yu Halos, 243 



b. Mature sheath becoming fibrillose at the ends (c). 



b. Mature sheath not fibrillose or rarely so (d). 



c. Filaments 4^ in diam.; yellowish or gjeenish; parasitic, 



sejunctum, 243 



Filaments lo-n/* in diam.; bluish green; on wet rocks,^/w0, 244 

 Thallus subglobose or fusiform, blackish, firm; filaments bluish, 

 diam. 6-7 jj. elongatum, 243 



d. Not subglobose; filaments straight, bent or curved, arugineum, 241 



83. ISACTIS. 



a. Filaments closely compacted, suddenly acuminate . fluviatilis, 244 

 a. Filaments erect, awl-shaped ctzspitosa, 245 



84. GLCEOTRICHIA. 



Sheath irregularly constricted; variable in size and form, natans, 246 

 " close, simple, not inflated nor constracted, subspherical, 



pis um, 247 







85. RIVULARIA. 



a. Sheaths inconspicuous; filaments clustered, base about 7 JA diam., 



echinulata, 249 



a. Sheaths distinct; filaments some apparently withered, others more 

 swollen, base 8-9yw diam dura, 249 



