PEDIASTRUM. 69 



belong to the genus Ankistrodesmus, and there is 

 but one species, falcatus. 



The next genus, Pediastrum, is composed of 

 many species, all being more or less like a star ; 

 they are formed of several little cells, four or 

 more united together either in a single or double 

 circle : they are very curious, and soon attract 

 notice. I shall only give two species, which I 

 have myself seen repeatedly P.pertusum (Drop I. 

 fig. 11) and P. Napoleonis (Drop I. fig. 12) : the 

 figures show their extraordinary forms more 

 clearly than any words. 



Scenedesmus comprises little objects composed 

 of from two to ten minute cells, arranged in a 

 row, instead of in a circle, as in the last genus. 

 8. quadricaudata (Drop I. fig. 13) is common. 



