No. IO.] FRESH-WATER ALG/E. 33 



Propagation by means of autospores, which are formed, usu- 

 ally to the number of four or eight, in the mother-cell. 



T. minimum (A. Br.) Hansg., Fig. 23. 



T. trigonum var. punctatum (Kirch.), Fig. 24. 



T. trigonum var. pentagonum (Rab.), Fig. 25. 



SUB-FAMILY III. OOCYSTIDE.E. 



Cells spherical or elliptical, often retained within the swollen 

 wall of the mother-cell. There may be one or several parietal 

 chloroplasts. The cell wall of all but Palmellococcus is firm. 

 Multiplication by means of autospores, which often develop 

 and grow to full size in the mother-cell. 



Key to Genera. 



1. Cells curved, subcylindrical or sublimate. .Nephrocytium* 



Cells ellipsoidal Oocystis 



Cells spherical 2 



2. Cells large, solitary and free-floating. . . . Eremosphcera 

 Cells minute, forming a thin stratum. . . .Palmellococcus* 



Description of Genera. 



Nephrocytium Nag. Two, four, eight, or sixteen oblong 

 or kidney-shaped cells, associated in a free-swimming family, 

 surrounded by an oval or kidney-shaped covering. Of variable 

 size ; cells bright green. Frequent in ponds. Multiplication by 

 autospores, which are often spirally disposed around the inside 

 of the wall of the mother-cell. 



N. Ncegelii A. Br., Figs. 26, 29. 



A T . Agardhianum Nag., Fig. 27. 



Oocystis. This genus differs from Nephrocytium in 

 having cells ellipsoidal and showing polar nodules. There are 

 usually several parietal chloroplasts in each cell. 



Eremosphaera D. By. ( Chlorosphaera Henfrey). Large, 

 spherical, free-swimming cells, with firm walls, showing a 

 colorless border. Cell contents green, granulose; each cell 

 containing large numbers of small parietal chloroplasts. Mul- 

 tiplication into two or four parts, which escape through the 

 cell wall. Found in small pools. 

 3 



