CHARACIUM. 177 



lateral, more rarely terminal, pore or rupture ; oblong with two 

 vibratile cilia. A.Br. 



CHARACIUM SESSILE, Herm. 



Cell globose or broadly ovate, with apex somewhat pro- 

 duced ; one-half longer than broad, green ; cytioplasm often 

 concentrated or contracted in the middle. 



Diameter, 7-9 //. 



Frequent on filamentous algae. 

 Plate CLIX, fig. 1, five cells nearly matured. 



CHARACIUM ACUTUM, A. Br. 



Cells straight, usually erect, ovate, tapering gradually at 

 both ends, producing a short neck at the apex and a stipe at 

 the base ; apex at first acute and closed, later open to admit 

 the escape of the zoospores ; stipe short, dilated at the end, 

 cytioplasm homogeneous, or granular, pale-green, contracts 

 and then divides producing zoospores. 



Diameter of cells, 7-10 //. 



Syn. Hydrianum acutum, Eab. 



Parasitic on larger forms of the algae ; ponds. 

 Plate CLIX, fig. 2, four cells scarcely separable from the 

 preceding, C. sessile, except that it is shortly stipitate. 



CHARACIUM PRINGSHEIMII, A. Br. 



Cells erect or suboblique, upper end drawn out into a 

 rather thick neck ; stipe brownish yellow, dilated at the 

 base. Diameter of cells, 10-15 /* ; about twice as long as 

 wide ; cell contents green, granular. 



Differs from the last two in larger size and longer stipe. 



The features of the last three forms are so similar, the pro- 

 priety of separating them as species may be questioned. 

 Farther observations are desirable. 



Plate CLIX, fig. 3, three cells on filament of Oedogonium. 



CHARACIUM AMBIGUUM, Herm. 



Cells erect, more or less oblique, narrow lanceolate, some- 

 what sword-shaped, 4-6 times longer than broad, each end 

 attenuated, apex cuspidate and sometimes curved ; cytio- 

 plasm bright green. 



Diameter, 5-8 /*. 



Ponds and pools, rare. 

 Plate CLIX, fig. 5, six cells on filament of Conferva. 



