L 



Mi 



M 



I &!& 



Figure 169 



HOW TO KNOW THE FRESH-WATER ALGAE 



236a Cells elongate-cylindric, the apical cell unsymmetrically pointed. 

 Fig. 169 URONEMA 



Fig. 169. Uronema elonga- 

 tion Hodgetts. 



This is the only species 

 in a genus of question- 

 able position. The cells 

 are long and cylindrical with a [/ioihrix-like chloroplast. Usually the 

 filament is only a few cells in length. The unsymmetrically pointed 

 apical cell is the chief identifying character. Young stages in the de- 

 velopment of Sfigeoclonium plants should be kept in mind when identi- 

 fication of Uronema is made. 



236b Cells short-cylindric, apical cell not tapering. See Fig. 167.... 

 ULOTHRIX 



237a (225) Cells quadrate or oval to subglobose, inclosed in a strati- 

 fied gelatinous sheath. Fig. 170 CYL1NDROCAPSA 



Fig. 170. Cylindrocapsa geminella var. minor 

 Hansg. a, portion of filament with oogonia; 

 b, vegetative cells. 



Although filaments of this genus begin as 

 attached plants they soon become free-float- 

 ing and are found intermingled with other 

 filamentous algae, especially in soft water or 

 acid lakes. The chloroplasts are so dense 

 and the cell contents include so much food 

 storage material that few structural charac- 

 teristics can be determined. The female re- 

 productive organs are globular and greatly 

 swollen, often red in color, as are the an- 

 theridia which occur as series (sometimes 

 double) of smaller cells. 



108 



