HOW TO KNOW THE FRESH-WATER ALGAE 



169a Cells enclosed by a mucilaginous sheath 170 



169b Cells not enclosed by a sheath 171 



170a Cells eccentrically placed in a sheath which has numerous lamel- 

 lations (layers); pyrenoid lacking. Fig. 124 UROCOCCUS 



Fig. 124. Urococcus insignis (Hass.) Kuetz. 



-•'•■.: 



Although holding a place in the Tetra- 

 sporales according to its assignment in the 

 past, this reddish-colored cell has been 

 shown to be an encysted stage of one of 

 the motile Dinoflagellates (Pyrrhophyta). 

 Unless other species are shown to be 

 separable and distinctive, the genus may 

 be reduced to synonymy. 



Figure 124 



170b Cells centrally placed in a sheath which has few or no lamella- 

 tions; pyrenoid present; (usually colonial, sometimes solitary). See 

 Fig. 41 GLOEOCYSTIS 



171a (169) Chloroplast 1; cells solitary (often gregarious) 172 



171b Chloroplasts more than 1; (cells usually ellipsoid in a gregarious 

 association but sometimes round). Fig. 125. PALMELLOCOCCUS 



Figure 125 



Fig. 125. Palmellococcus miniatus (Kuetz.) Chod. a, habit of colony; 

 b, portion of colony showing cells with Chlamydomonas-\ike chloro- 

 plast. 



These oval or spherical cells usually occur as films on moist sub- 

 strates (rocks, cement walls, etc.). There are 1 to several chloroplasts 

 without pyrenoids. Reproduction is by the formation of autospores 

 (Chlorococcales). Identification is difficult unless the organisms are 

 cultured because there are so many minute green cells which might 

 be confused with th^s genus. 



82 



