66 SPECIES OF ALG^. 



a. Branches polymorphous (6). 



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 50//. Alpine Crameri, 273 



d. " " " less than 50/^ (e). 



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

 e. Cells small, not moniliform (y^). 



/. Filaments flexuous, curved, not rigid, branched, i6-i7yu, 



scytonematoides, 271 

 /. " 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 15/* {Ji). 



b. Cells about as long as wide; filaments io-i2yU . . Braunii, 275 

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



tcnuissimus, 277 



b. Cells equal to twice as long as wide; filaments 8-1 lyu 



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). 



