SPECIES OF ALG^. 63 



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



15-20/^ . . ... lacucola, 239 



b. Attached (c). 



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



c. Ends tapering, or hair-pointed {d'). , 



d. Forming a stratum (/). 

 d. Forming tufts {g). 



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

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



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



diating; sheath up to 30yu, wide radiosa, 239 



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



Brebissonii, 23 S 



82. MASTIGONEMA. 



§ Filaments rounded or truncate at apex (a). 



§ " tapering to a hair-point (b). 



a. Sheath thick, apex truncate, open; diam. Zjx . fertile, 244. 



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



cate; diam 12 jj. . . . . ... 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 greenish; parasitic, 



sejunctttm, 243 



c. Filaments lo-ii/^ in diam.; bluish green; on wet xock=,, fibrosa, 244 



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



diam. 6-7/* ... ... elongatum, 243 



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



83. ISACTIS. 



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

 a. Filaments erect, awl-shaped caspitosa, 245 



84. GLCEOTRICHIA. 



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

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



pisum, 247 



85. RIVULARIA. 



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



echitiulata, 249 



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



swollen, base 8-9/* diam. . dura, 249 



