WISCONSIN PHYTOPLANKTON 31 



a thick, hyaline, markedly lamellate, gelatinous envelope. Envelope of 

 individual cells conspicuous, lamellated. Cell contents distinctly gran- 

 ulose, bright blue-green. (Tychoplanktont). 



Diam. cells (without sheath) 54-58 p.; (with sheath) 67-70 ft. 



Mary (rrr). 



CHROOCOCCUS TURGIDUS (Kiitzing) Nageli. PI. 1, Fig. 9. 

 Gatt. einz. Algen 46. 1849; G. S. West, Brit. Freshw. Algae 352, fig. 166 B - 1904. 



Cells hemispherical, spherical, ovoid, or somewhat flattened by mutual 

 compression. Cells solitary or in colonies of 2-4 (rarely 8) enclosed 

 by a thick, hyaline, generally lamellated, gelatinous sheath. Individual 

 cells also with hyaline, lamellated sheaths. Cell contents homogeneous 

 or finely granulose ; pale to bright blue-green or rarely brownish in 

 color. ( Tychoplanktont) . 



Diam. cells (without sheath) 8-32 /A; (with sheath) 13-40 /*. 



Beasley (rrr), Beaver (2) (rr), Browns (IT), Hillman (rr), Horse (rrr), 

 Oconomowoc (rr), Otter (rr), Rudolph (rr), Sand (2) (rr), Upper Turtle (rr), 

 Waubesa (rrr). 



MERISMOPEDIA Meyen 1839. 



Colonies always forming flat, curved, or irregularly twisted plates 

 one cell in thickness with the constituent cells in rectilinear series and 

 usually in groups of four. Cells spherical to subspherical with rounded 

 ends, hemispherical for some time after division. Individual sheaths 

 of cells rarely distinct, generally confluent with the copious, hyaline, 

 homogeneous, colonial envelope. Number of cells in colony 1 4000, 

 cell number a multiple of two in young colonies, not a multiple of two 

 in old colonies. Cell contents generally homogeneous, rarely with 

 pseudovacuoles. Color varying from grey through light to bright blue- 

 green, rarely rose pink to violet. 



KEY TO THE SPECIES. 



Cells bright blue-green M. ELEGANS 



Cells pale blue-green. 



Cells some distance from one another M. PUNCTATA 



Cells close together (not mutually compressed). 



Diameter of cells 1. 5-2 /* M. TENTJISSIMA 



Diameter of cells 3-6 /* M. GLAUCA 



