WISCONSIN PHYTOPLANKTON 103 



Chloroplast of young cells single, laminate, parietal, with one pyrenoid ; 

 diffuse in old cells. 

 Reproduction, aside from vegetative cell division, unknown. 



GLOEOCYSTOPSIS LIMNETICUS G-. M. Smith. PI. 20, Figs. 1-2. 

 Bull. Torr. Bot. Cl. 43: 475, pi. 24, fig. 12. 1916. 



Cells 4r-6 fL broad, 10-15 /* long. Cell aggregates 25-30 /t in diam. ; 

 colonies up to 125 /A in diam. (Euplanktont). 



Bear Trap (rr), Beaverdam (rrr), Catfish (IT), Harris (rrr), Little Bass 

 (2) (rrr). 



A species that combines the general external morphological character- 

 istics of Gloeocystis and the cell shape of N ephrocytium. 



PLANKTOSPHAERIA G. M. Smith 1918. 



Cells spherical, embedded in a copious, homogeneous, hyaline, gelat- 

 inous envelope. At first solitary, later irregularly distributed within 

 the gelatinous envelope. Mature cells with several parietal, polygonal, 

 flattened chloroplasts each of which contains a single pyrenoid. 



Reproduction by liberation of daughter colonies through the breaking 

 down of the gelatinous colonial envelope. 



PLANKTOSPHAERIA GELATINOSA G. M. Smith. PI. 20, Figs. 3-6. 

 Trans. Wis. Acad. Sci., Arts, & Lett. 19 l : 627, pi. 10, figs. 8-11. 1918. 



Specific characters as described above. (Euplanktont). 

 Diam. cells 4.5-25 p ; colonies up to 150 p. in diam. 

 Browns (rr), Mendota (r). 



The general appearance of the colony suggests Spha&rocystis 

 Schroeteri but P. gelatinosa differs in the numerous parietal chloroplasts 

 of each cell. 



ASTEROCOCCUS Scherffel 1908. 



Cells spherical or sub-spherical, solitary or in colonies, with a wide, 

 homogeneous or lamellated, gelatinous envelope. Chloroplast single, 

 central, star-shaped, the astral radiations ending in a disc at the cell 

 wall. Pyrenoid single, at the center of the chloroplast. Certain species 

 with two peripheral vacuoles and an eyespot. 



Asexual reproduction by vegetative cell division and biciliate sub- 

 spherical zoospores. 



Sexual reproduction unknown. 



