- 241 — 



1895, p. 271, Pl. IV, figs. 31-33), which has been supposed to be a 

 stage of Aphanizomenon flos aquœ (L.) Ralfs., and perhaps it is also the 

 case with the form in question; but the cells are larger than those in 

 Klebahn's form. 



Coelosphærium Nægelianum Unger. This form has been figured by 

 Borge (Schwedisches Süsswasserplankton, Botaniska Notiser 1900, Pl. I, 

 fig. 5); the cells contain „ floating-bodies" and are arranged in a sphere, 

 the mucilage of which has a radiating structure, especially when treated 

 with m ethyl en-blue. 



Chroococcus limnetic us Lemm. is a very characteristic alga. Lem m e r - 

 mann has given a good figure of it in Forschungsber. d. biolog. Station 

 zu Plön VII, 1899, Pl. I. 



Microcystis incerta Lemm. and P. stagnalis Lemm. — I am not quite 

 sure of the correctness of the determination of these two species, but the 

 specimens examined agree well with the short descriptions and the figure. 



