HOW TO KNOW THE FRESH-WATER ALGAE 



26b Cell wall smooth, without flanges 



29 



27a- Envelope roughened or warty, the flanges forming 4 lobe-like ex- 

 tensions when seen from the top or side. Fig. 22 



WISLOUCHIELLA 



Fig. 22. Wislouchiella planctonica Skvor. a, 

 'front' view; b, side view. 



Named for the biologist Wislouch, this bi- 

 flagellated organism is identified quickly by 

 the oddly-shaped lobes or processes of the 

 wall which extend in several planes. Rare. 



Figure 22 



27b Envelope not roughened, or if roughened, without lobe-like ex- 

 tensions 28 



28a Envelope composed of 2 overlapping pieces, the seam showing 

 when the vegetative cell is seen from the side. Fig. 23. 



PHACOTUS 



Figure 23 



Fig. 23. Phacotus lenticularis (Ehr.) Stein. 

 a. 'front' view; b, side view showing bi- 

 valve structure of cell wall. 



This genus is relatively rare, but is often 

 abundant in collections from habitats where 

 it occurs. It is both euplanktonic (a true 

 plankter) and tychoplanktonic and may oc- 

 cur in river as well as in lake collections. 



32 



