Plate 50 



Pediastrum Kawraiskyi Schmidle, x 333 ( after Smith ) 



Pediastrum simplex (Meyen) Lemmermann, x 500 



Pediastrum tetrcis ( Ehrenb. ) Ralfs, x 1000 



Pediastrum simplex var. duodetiarium (Bailey) Raben- 

 horst, X 500 



Pediastrum tetras ( Ehrenb. ) Ralfs, x 1000 



Pediastrwn tetras var. tetraodon (Corda) Rabenhorst, 

 X 1000 ( redrawn from Smith ) 



Fig. 8. Sorastrum americanum ( Bohlin ) Schmidle, x 500 ( re- 



drawn from Smith ) 



Fig. 9. Sorastrum spinulosum Naegeli, x 750 (after Smith) 



Fig. 10. Sorastrum americanum var. unduhtU7n G. M. Smith, x 

 750 (after Smith) 



760 



