HOW TO KNOW THE FRESH-WATER ALGAE 

 357b Cells not crescent-shaped 358 



358a Cells broadly oval, ovate, or obovate, with a truncate or bilobed 

 anterior end; flagella 2, attached at the anterior end; chromato- 

 phores 2, lateral elongate plates 359 



358b Cells shaped otherwise; flagella not anterior 



360 



359a Cells without a gullet in the anterior end, but with a slight apical 

 depression. Fig. 254 CHROOMONAS 



Fig. 254. Chroomonas Nordstedtii Hansg. 



These minute, slipper-shaped organ- 

 isms have 2 parietal, blue chromato- 

 phores, and 2 flagella that are attached 

 just below the apex of the cell. They 

 move rapidly and determinations can- 

 not be made unless some medium is 

 introduced to the mount to slow down 

 their action. Use 5% glycerin. 



Figure 254 



359b Cells with a gullet. 



Figure 255 



Fig. 255 CRYPTOMONAS 



Fig. 255. Cryptomonas erosa Ehr. 



There are probably several species of 

 this genus, but few are reported prob- 

 ably because they are easily overlooked 

 among dense mixtures of algae where 

 they mostly occur. The cells are rela- 

 tively larger than Chroomonas (Fig. 254) 

 and have a gullet at the anterior end 



which can be seen as the cells rotate on their axis. 



150 



