HO WISCONSIN PHYTOPLANKTON 



Subfamily OOCYSTEAE. 



Cells spherical, ovoid, or renif orm ; solitary or in temporary colonies. 

 Daughter cells retained within old mother cell wall for some time after 

 their formation. Walls generally thick and cells with one to many 

 ehloroplasts. 



KEY TO THE GENERA. 



Cells within old mother cell wall separated by a dark gelatinous 



mass GLOEOTAENIUM 



Cells within old mother ceil wall not separated by a dark gelat- 

 inous mass. 



Cells ovoid to elliptic, never curved OOCYSTIS 



Cells ovoid to renif orm, frequently curved NEPHBOCTTITJM 



OOCYSTIS Nageli 1845. 



Cells ovoid, ellipsoid, or cylindrical with rounded to somewhat pointed 

 ends, generally symmetrical but never curved. Cell wall smooth, with- 

 out spines, frequently with nodular thickenings at the poles. Chloro- 

 plasts one to many; parietal, disciform, stellate, or reticulate; with or 

 without pyrenoids. Cells solitary or in temporary colonies of 2-4-8-16 

 or more enclosed by the partially gelatinized and greatly swollen old 

 mother cell wall. 



Eeproduction by a formation of 2-4-8-16 autospores that remain 

 within the old cell wall for some time. Three to four cell generations 

 sometimes enclosed by the same wall. Tetraedron-like resting spores 

 with granulate walls have been observed. 



The genus differs from others in the expanded cell wall that encloses 

 the cells in temporary colonies. Printz (Nyt. Mag. f. Naturvidensk. 

 1913, p. 165) has recently monographed the genus and cleared up many 

 points by collecting the published descriptions of species; but there is 

 great need of a series of cultural studies to determine the range of 

 variation within the so-called "species" that are recognized at the 

 present time. 



KEY TO THE SPECIES. 



Chloroplast stellate O. NATANS 



Chloroplast disciform to laminate. 

 Cells with polar nodules. 



Sides of cells concave O. PANDTJRIFOKMIS 



Sides of cells convex. 

 4 or more ehloroplasts in each cell. 

 Cells with 40-60 ehloroplasts 0. EBEMOSPHAERIA 



