SPECIES OF ALG^. 67 



a. Without mucilage; filaments in irregular masses, coiled, 



tenuissimum, 282 



a. With .mucilage; joints equal, rather distant . . comminutum, 282 



b. Soft, becoming gelatinous cushions (if). 



b. " " tongue-shaped, plane, irregularly expanded {i). 



b. With a firm coating (/). 



c. Fronds with a firm coating (^). 



d. Mature frond suborbicular, often perforated and expanded, 



commune, 283 



d. " " linear, straight, long; filaments parallel, 



flagelliforme, 285 



e. Globose thalli within a subspherical gelatinous mass, muscorum, 282 

 e. Globose, firm; filaments olive . . . . . Aumifusum, 282 

 e. Suborbicular, soft; filaments bluish green . . . calcicola, 283 

 /. Globose, firm, coating brownish; joints -subspherical, 



sphcericum, 283 

 /. " soft, sheath often colored and general mucus colorless, 



rupestre, 283 

 /. " not I mm in diam.; cells cylindrical, slightly constricted, 



macrosporum, 284 

 g. Cells of two kinds, unequal (K). 

 g. Cells uniform, regular [t). 



h. One kind elongated, the other spherical; bluish . cceruleum, 284 

 i. Fronds globose, from 2 mm to size of a cherry . pruniforme, 284 

 /. " rounded or discoid, becoming hollow (/), 

 / Fronds subglobose, warty, brownish green . . verrucosum, 284 

 /• Fronds suborbicular, erect, smooth, tenacious . . Alpinum, 285 



94. ANAB^NA. 



§ On tree trunks, near the water's edge, bluish . cupressaphila, 288 

 § In brackish ditches; stratum bluish .... oscillarioides, 288 

 § In sweet waters (a), 

 a. Cells 3-4 yw in diameter [b). 



a. Cells 4-ii/<in diameter {c). 



b. Deep blue green; filaments curved, almost parallel, 



variabilis, 287 



b. Pale bluish, sometimes yellowish; filaments curved, usually in 



clusters . . .... ... . stagnalis, 288 



c. Filaments curved, often coiled ... ... flos-aqua, 286 



c. Filaments straight, often coiled when young . . gigantea, 287 



