HOW TO KNOW THE FRESH-WATER ALGAE 



11a Cells round, oval or pear-shaped, rigid, fixed in shape when 

 swimming; paramylum in the form of 2 large lateral rings; tail- 

 piece, if present, usually in the form of a short, sharp protrusion 



from the rounded posterior end of the cell. Fig. 7 



LEPOCINCL1S 



Fig. 7a. Lepocinclis acuta Presc, showing 

 spiral markings of the periplast (mem- 

 brane); b, Lepocinclis glabra fa. minor 

 Presc, showing four lateral, band-like 

 paramylum bodies. 



Round when seen on end, rather than 

 flat like Phacus (Fig. 6). The siorage ma- 

 terial in most species forms 2 rings that 

 lie along the side walls of the cell. Often 

 with Euglena (Fig. 8), but much more ac- 

 tive. 



Figure 7 



lib Cells often changing shape when swimming (rigid in some spe- 

 cies), elongate, nearly cylindrical, or fusiform; paramylum in the 

 form of a few and large, or numerous, small, colorless rods or 

 sticks; tail-piece formed by gradual narrowing of the cell. Fig. 8. 

 EUGLENA 



Fig. 8a. Eugiena convoiufa Korsch., 

 showing lateral paramylum plates as 

 seen on edge, one in flat view; b, E. 

 elastica Presc. Both of these are meta- 

 bolic species (changing shape while 

 in motion) whereas some forms are 

 rigid. 



Although usually green, these elon- 

 gate, slowly moving species sometimes 

 are colored red because of a pigment, 

 haematochrome. A pond or slough may 

 have a bright red film over the surface 

 caused by Euglena which seem to pro- 

 duce the pigment in response to intense 

 light. 



Figure 8 



12a (8) Plant a colony of 4 or more cells, either closely adjoined, or free 



from one another within a gelatinous envelope 



Division CHLOROPHYTA (in the main) 13 



12b Plant a solitary cell 22 



25 



