No. IO.] FRESH-WATER ALG/E. 65 



6\ spinosum Delp., Figs. 120, 277. 

 S. pulcrum Bailey, Fig. 271. 



Onchonema Wall. Like Spharozosma except that the 

 granular processes are long. 



0. serratum (Bailey) Wall., Fig. 272. 



Hyalotheca Ehrb. Cells short, cylindrical, usually 

 blunted, constricted in the centre; joined in long filaments en- 

 closed in an ample mucilaginous sheath. The end view of the 

 cell is round and shows the chloroplast to be eight- to ten-rayed. 



H. dissilicns (Sm.) Breb., Fig. 273. 



Spondylosium Breb. (Leuronema Wallich). Like 

 Spharozosma except that instead of being united by lateral 

 processes, the cells are joined in filaments merely by the close 

 apposition of the cells. 



5". papillatum West, found but not figured. 



Desmidium Ag. (Didymoprium Kiitz.; Aptogonum 

 Ralfs). Cells incised or entire, with two chloroplasts barely 

 touching in the middle ; triangular or quadrangular in end 

 view; united into fragile, elongated filaments, regularly 

 twisted, and enclosed in a mucous envelope. 



D. cylindricum Grev., Fig. 276. 



D. Swartzii Ag., Fig. 275. 



Gymnozyga Ehrb. (Bambusina Kiitz.). 1 Cells barrel- 

 shaped with one or more narrow bands around the middle ; 

 closely united into articulate filaments. Chlorophyll bodies as 

 in Hyalotheca. Zygospores smooth, ellipsoidal. 



FAMILY II. ZYGNEMACE^E. 



Unbranched filaments composed of single cells or of a 

 simple series of cells. Chloroplasts in the shape of spiral 

 bands, axile plates, or twin stellate bodies. 



Key to Sub-families. 



Conjugation producing a zygospore which, after a 

 period of rest, develops directly into a new gameto- 



phyte ZYGNEMEiE 



5 



