66 SPECIES OF ALG^E. 



a. Branches polymorphous (b). 



a. Branches not polymorphous (d). 



b. Apices obtusely rounded (c). 



b. " attenuate, or filaments with scattered spines, Alpinus, 269 



c. Plants attached only by the mucus surrounding them, 



pulvinatus, 268 



c. Plants firmly attached to rocks and stones . . coralloides, 270 



d. Diameter of filaments about 5o/v. Alpine .... Crameri, 273 



d. " " u less than 50/4 (e). 



e. Cells broadly ovate, moniliform; on wet rocks . compactus, 271 



e. Cells small, not moniliform (/). 



f. Filaments flexuous, curved, not rigid, branched, i6-i7/./, 



scytonematoides, 271 



f. " short, intricate; branches many, irregular (g). 



g. Mature sheath deep reddish brown, of branches yellowish, apices 



colorless argillaceus, 274 



g. Mature sheath colorless, hyaline, rarely light yellow crustaceus 274 



92. HAPALOSIPHON. 



Aquatic, often parasitic (a], 

 On tree trunks (c). 

 On wet rocks(^). 



a. Diameter of filaments about 15^; much branched, bluish; sheath 

 often yellowish brown Brebissonii^ 276 



a. Diameter of filaments less than i5yu (b). 



b. Cells about as long as wide; filaments io-i2// . . Braunii, 275 

 b. Cells about as long as wide; filaments 7-8yw, branches 3-4/f, 



tcnuissimus, 277 



b. Cells equal to twice as long as wide; filaments 8-n// 



fuscescens, 277 



c. Filaments 20-25^, branches rather thinner . . . byssoideus, 276 



d. Filaments apt to be solitary, cells moniliform, bluish, 



torulosus, 276 



93. NOSTOC. 



Fronds soft, often without definite form (A). 



Fronds globose or nearly so, or discoid or linear, often irregular 

 with age (B). 



A. Aquatic (a). 



B. Aquatic (c). 

 B. Terrestrial (b). 



