a mucilaginous sheath. Vegetative cells spherical or compressed at 

 the poles, (10)-12-14-(15)/x, in diameter. Heterocysts globular, 

 10— 14/x in diameter. Gonidia broadly ovate, near to the heter- 

 ocysts or scattered, 17-20|U, in diameter, 20-30/a long. 

 Euplankter. Mich., Wis. 



Anabaena macrospora Klebahn 1895, p. 269 

 PI. 117, Figs. 4-6 

 Trichomes planktonic, straight or flexuous, solitary; cells globose 

 or somewhat ellipsoid, 5-6.5yu, in diameter, {5)-6-8-{9) fi long; 

 heterocysts spherical, about G/x in diameter; gonidia globose to ovate, 

 angular in optical section, not adjoining heterocysts, 17— 18.5/x in 

 diameter, 24—26^ long. 



Plankter; in many hard and semi-hard water lakes. Wis. 



Anabaena macrospora var. robiista Lemmermann 1898d, p. 154 



PI. 117, Fig. 7 



Trichomes planktonic and solitary. Cells globose or ellipsoid, 

 9.7-ll;U, in diameter. Heterocysts globose, 11.5/Lt in diameter, 11-12/a 

 long. Gonidia globose or ovate; scattered, or adjacent to the heter- 

 ocysts; 13.2-15/i in diameter, 27-28- ( 34 )/x long. 



Plankter; in several hard water lakes; often appearing in water 

 bloom associations in late summer. Wis. 



Anabaena oscillarioides Bory 1822, p. 308 

 PI. 117, Figs. 8-10 



Filaments straight, or entangled in a thin gelatinous layer or soli- 

 tary. Cells barrel-shaped or truncate-globose, 4— 6ya in diameter, 

 7.8-8/^ long. Heterocysts round or ovate; 6-8/x in diameter, (6)- 

 9.2-{l0)fx long. Gonidia cylindrical; developing on both sides of 

 the heterocyst (rarely on one side only); 8-10-(15.2)/a in diameter, 

 20-40- ( 76 )/t long. 



Spores in our specimens are larger than those originally described 

 for this species. 



Forming thin films on submerged aquatics, or subaerial in swampy 

 places and along margins of lakes. Mich., Wis. 



Anabaena planctonica Brunnthaler 1903, p. 292 

 PI. 118, Figs. 1-3 

 Trichomes solitary, free-floating, inclosed in a wide gelatinous 

 sheath; cells barrel-shaped or spherical, 9-15ju, in diameter, 6.5-10/a 

 long, with pseudovacuoles; heterocysts spherical, with lateral 'wings' 

 of mucilage, 9— llyu, in diameter; gonidia ellipsoid, 10—14/* in diam- 

 eter, 15— 30/t long, near or remote from the heterocysts. 

 Plankter; in lakes. Wis. 



[517] 



