136 WISCONSIN PEYTOPLANKTON 



Cells 1-2.5 fi broad ; 20-40 p long. 

 Grassy (rr), Silver (2) (rrr). 



G. S. West places the alga as a variety of A. falcatus but the twist- 

 ing of the cell seems to be such a constant character that I have fol- 

 lowed Lemmermann 's practice in considering it a distinct species. 



CLOSTERIOPSIS Lemmermann 1898. 



Cells solitary, acicular, with ends produced into very acute apices, 

 without a gelatinous envelope. Chloroplast single, not interrupted 

 at the center of the cell, occupying the greater portion of the cell and 

 containing a single axial row of about a dozen pyrenoids. 



The genus is very closely related to Ankistrodesmus, differing only 

 in the greater length of the cells and the axial row of pyrenoids. It 

 also resembles certain Closterium species but the chloroplast of Closter- 

 ium is always interrupted at the center of the cell. Many feel that the 

 single species is not sufficiently differentiated to warrant its separation 

 from Ankistrodesmus. 



CLOSTERIOPSIS LONGISSIMA var. TROPICA W. & G. S. West. PI. 32, Fig. 8. 



Trans. & Proc. Bot. Soc. Edinb. 23: 31, pi. 1, fig. 1. 1905. 



Rhaphidium longissimum var. tropicum W. & G. S. West, Trans. Linn. Soc. 

 2nd. .Ser. Bot. 6: 198. 1902. 



Cells acicular, poles acute but not ending in a point of hair-like fine- 

 ness. (Facultative Planktont). 



Cells 6-7.5 fjL broad ; 225-370 ^ long. 



North Turtle (rr). 



The dimensions of specimens that I have found agree with those given 

 for individuals from Ceylon but not with those from the Scotch plank- 

 ton. 



SCHKOEDERIA Lemmermann 1898. 



Cells solitary, straight or curved, acicular; with one apex produced 

 into a fine seta tapering to a point, the other with a slightly broader 

 projection terminating in a small disc. Cells without a gelatinous en- 

 velope. Chloroplast single, parietal, laminate ; with one pyrenoid. 



Method of reproduction unknown. 



