HOW TO KNOW THE FRESH-WATER ALGAE 

 34b Cells oblong or ovoid, without lobes. Fig. 32 DUNALIELLA 



Fig. 32. Dunaliella salina Teodor. Two differently- 

 shaped individuals. 



This species and D. viridis Teodor. are appar- 

 ently the only ones described thus far for the 

 genus, but they are widely distributed judging 

 from reports of them in different parts of the 

 world, occurring in brackish or saline waters. 



Figure 32 



35a (6). Plant a filament (cells in continuous or interrupted series) 

 with or without branches; or a flat expanse or attached cushion 

 with the branches closely oppressed so that the basic filamentous 

 plan is not clearly evident; or a tubular, thread-like thallus without 

 cross walls (coenocytic) 189 



35b Plants not filamentous, but solitary cells or a colony of 2 or more 

 cells inclosed by mucilage or by an old mother cell wall (see Oocy- 

 stis. Fig. 85), or cells variously adjoined to one another (Scenedes- 

 mus. Fig. 74; Pediastrum, Fig. 70) 36 



36a Cells solitary or gregarious but not adjoined to form colonies. .109 



36b Cells adjoined or arranged in colonies 



37 



37a Colony composed of 2 trapezoidal cells adjoined along their broad 

 bases. Fig. 33 EUASTROPS1S 



Figure 33 



Fig. 33. Euastropsis Richteri (Schmid.) Lag. 



This is the only species of the genus on rec- 

 ord. The two cells which compose the colony 

 appear much like those of Pediastrum (Fig. 70) 

 but are never more than this number joined 

 together. Euastropsis occurs in the tychoplank- 

 ton; is rare but widely distributed. 



36 



