PLATE VI. 



Pig. ] Micrasterias americana. 



" 2 Spirotaenia condensata. 



a, resting spore. 



3 Sphaerozosma filiforme. 



4 Sphaerozosma serratuni. 



6 Desmidium swartzii. 



a, end view. 



7 Desmidium aptogonium. 



a, form. 



8 Staurastrum pseudopachyrhynchium. 



a, end view; b, end view. 



9 Closterinm dianae. 



10 Closterium jenneri. 



a, cell with chloroplasts. 



11 Arthrodesmus octocornis. 



a, end view. 



12 Arthrodesmus octocornis. 



a, end view. 

 13, cells in process of fission.. .Xanthidium fasciculatum. 

 14 Xanthidium fasciculatum. 



