58 WISCONSIN PHYTOPLANKTON 



ANABAENA LEVANDERI Lemmermann. PI. 8, Figs. 4-5. 

 Ber. d. D. Bot. Ges. 24: 536. 1906. 



Filaments solitary, free-floating, straight or slightly flexed, not en- 

 closed by a gelatinous sheath. Trichomes cylindrical, slightly con- 

 stricted at the cross walls of the cells. Vegetative cells twice as long as 

 they are broad, cylindrical, with rounded ends. Heterocysts hyaline, 

 spherical or ellipsoid. Spores solitary, adjacent to or remote from the 

 heterocysts, twice as broad as the vegetative cells, ellipsoid in shape. 

 Cell contents rarely homogeneous and pale blue-green to grey ; usually 

 with numerous pseudovacuoles. (Euplanktont). 



Cells 4-6 n broad, 11-33 p. long ; heterocysts 6.5-8 p. broad, 6.5-9.5 ^ 

 long ; spores 8-15 p. broad, 19-45 p. long. 



Chain (sss). 



The dimensions of all specimens found in Chain lake have been near 

 the minimal limits set by Lemmermann. 



ANABAENA BORNETIANA Collins. PI. 8, Fig. 3. 

 Erythrea4: 120. 1896. 



Filaments free-floating, straight or slightly curved. Vegetative cells 

 spherical or slightly shorter than they are broad, with homogeneous 

 pale blue-green contents. Sheaths of trichomes very delicate. Hetero- 

 cysts spherical to elongate. Spores elongate cylindrical, with rounded 

 ends, adjacent to and on both sides of, or remote from the heterocysts. 

 ( Tychoplanktont) . 



Vegetative cells 12 p, broad ; heterocysts 13-14 p. broad, 13-20 p. long; 

 spores 15-20 p. broad, 50-90 p. long. 



George (rr). 



Only a few filaments of this species were found in George lake and 

 these contained but few spores which were not always adjacent to the 

 heterocysts. The species may, therefore, not be A. Bornetiana for Col- 

 lins states that the spores are always adjacent to the heterocysts. 



ANABAENA AUGSTUMALJS var. MARCHICA Lemmermann. PI. 8, Figs. 9-10. 

 Forschungsbr. a. d. Biol. Stat. zu Plon 12: 147. 1905. 



Filaments solitary, free-floating, more or less bent but not circinate, 

 without a gelatinous envelope. Vegetative cells spherical, broadly ellip- 

 soid or cylindrical ; with numerous pseudovacuoles. Heterocysts spheri- 

 cal or slightly elongate. Spores remote from heterocysts, elongate cylin- 



