III. — Dksmids. I, Gonatozygon. 2, Spirot;enia. ,,, 4, Docidiuiii. 5, 6, 7, S, 

 Closterium. 9, Desuudiinn. 10, Mesotseniutn. 12, Nc-trium. 13, Stanraslrum 

 (end view. 14, Staurastrum (side view I. 15. Micrasterias. 16, Genicularia. 

 17, Peiiiuiii. iS, Micrasterias. 19, Tetmeniorus. 20, Pleurotienium. 21, 22, 

 Cosmariiun. 23, Penium. 24, Euastrum. 25, Cylindrocyslis. 26, Euastrum. 



