Oocystis elliptica W. West 1892, p.736 

 PI. 51, Fig. 11 



Colony composed of 4-8 oblong-ellipsoid cells inclosed by the 

 irregularly swollen old mother cell wall; poles of the cells broadly 

 rounded and without polar thickenings; chloroplasts numerous (as 

 many as 20) parietal discs, apparently without pyrenoids; cells 

 11-15.6/x in diameter, 20-21.4- (25)/. long. 



Common in the plankton of many soft water lakes and ponds; 

 frequent in ditches and swamps, especially where there are luxuriant 

 growths of algae and where the water is rich in organic acids. Mich., 

 Wis. 



Oocystis elliptica var, minor West & West 1894, p. 14 

 Cells smaller than in the typical plant, 7-10/i, in diameter, 15-22/i, 

 long. Common in plankton. Wis. 



Oocystis Eremosphaeria G. M. Smith 1918, p. 630 

 PI. 51, Fig. 12 



Plants unicellular, usually solitary, sometimes in a group of 2 or 

 4 within the old mother cell wall; cells narrowly ovate, the poles 

 broadly rounded and furnished with a large nodular thickening; 

 chloroplasts numerous, as many as 60 parietal, lenticular discs, each 

 with a pyrenoid; cells 20-25-(31)/a in diameter, 35-45/a long. 



The larger specimens always seem to be found in habitats where 

 there is a rich mixture of algae in shallow, warm water. 



Plankter; in many lakes and sloughs. Mich., Wis. 



Oocystis gigas Archer 1877, p. 105 

 PI. 51, Fig. 14 

 Plant usually a family of 4 broadly ellipsoid or ovate cells inclosed 

 within a much enlarged, elliptical mother cell wall; cells broadly 

 rounded at the poles, which are smooth and without nodules; 

 chloroplasts many parietal discs; pyrenoids not observed; cells 

 29-35- (40)/. in diameter, 40-51. 8/i long. 

 Rare; in plankton. Mich., Wis. 



Oocystis gloeocystiformis Borge 1906, p. 23 

 PI. 51, Fig. 13 



Plant usually composed of a family of 2 or 4 ellipsoid cells inclosed 

 within the old mother cell wall; cells with narrowed and sharply 

 rounded poles, without nodular thickenings; 1 parietal chloroplast in 

 each cell, pyrenoid lacking; cells (3)-ll/t in diameter, 8-18.5/t long. 



The poles of the cells of this species are somewhat produced to 



[244] 



