OPHIOCYTIUM. 175 



SdADIUM GKRACILIPES, A. Br. 



Simple umbels, in connection by means of a cell ; usually 

 floating ; a loose and vague growth ; cells cylindrical, 

 straight, rarely slightly curved (foreign plants sometimes 

 spirally twisted ) ; apices obtuse ; stems slight, with stipe 

 nearly twice as long as the diameter of the cell. 



Diameter of cells, 4-5 //. 



Only locality hitherto discovered, pool, Minnesota. 



Syn. Ophiocytium gracilipes, A. Br. 



Plate CLYII, figs. 7, 8, from a specimen, Minnesota. 



III. EREMOBiA.--The single cells do not remain together, but 

 scatter, and live independent of one another; if not widely 

 separated they may form clusters of irregular forms, but no 

 coenobia. 



Genus 47, OPHIOCYTIUM, Naeg. 



Cells cylindrical, straight, variously curved or circinate, at- 

 tenuate at one end into a thin, short stem or mucro ; sometimes 

 both ends rounded bearing each a longer or shorter spine, and 

 sometimes without spines. 



Foreign authors seem unanimous in declaring "One or the 

 other pole attenuated into a thin, short stem ; the other pole 

 rounded.'' Our forms, evidently belonging to the same genus, 

 diifer in this regard. 



Propagation by means of zoospores as in Sciadium with this 

 difference, that the daughter generations of the former remain 

 attached, in the present they are set free. 



OPHIOCYTIUM COCHLEARE, A.Br. 



Cells cylindrical, slender, pale-green, often very long, fili- 

 form, variously curved or circinate, one end attenuated into 

 a spine-like process acute or truncate ; other end rounded ; 

 contents homogeneous. 



Diameter of cells, 5-8 yu. 



Frequent in ponds of stagnant water. 



Syn. Ophiothrix apiculata, Naeg. ; Spirodiscus cochlearis, Eich. 



Plate CLYIII, figs. 8-14, the usual appearance of the 



plant. 

 12 



