Anahaena Bornetiana Collins 1896, p. 120 

 PL 115, Figs. 8, 9 

 Trichomes straight, planktonic and solitary; cells spherical or 

 compressed globose, contents densely granular or homogeneous, 

 ll-12fx in diameter; heterocysts nearly spherical, 10-12-(14)/x in 

 diameter, 12-14-(20)/a long; gonidia cylindrical, adjacent to the 

 heterocysts (often one on either side) or scattered, (12.8)-14-(20)/x 

 in diameter, (50)-66-90/i, long. 



Plankter; in lakes. Wis. 



Anahaena circinalis Rabenhorst 1852, p. 209 

 PI. 116, Figs. 1, 2 

 Trichomes planktonic, flexuous and contorted; solitary or entangled 

 to form floating clots which are easily visible to the unaided eye. 

 Cells spherical or depressed-globose from contact; 8-12-(14)/a in 

 diameter. Heterocysts spherical or compressed, 8-10/* in diameter. 

 Gonidia remote from the heterocysts, rarely adjacent; cylindric, 

 straight or curved; (14)-16-18/x in diameter, 22-30-(32)/a long. 



This species is very common and widely distributed. It is often 

 found associated with A. spiroides in the plankton of hard water 

 lakes. These two species, together with Microcystis aeruginosa and 

 Gloeotrichia echinulata, are conspicuous components of water 

 blooms during late summer periods. 



Anahaena circinalis may be differentiated from A. spiroides by 

 the shape of the spore when in the reproductive condition, by the 

 lack of regularity in the twisting of the trichome, and by the size of 

 the cells in the vegetative state. 



Mich., Wis. 



Anahaena circinalis \ sly. macrospora (Wittr. ) DeToni 1907, p. 445 



PI. 116, Figs. 5, 6; PI. 120, Fig. 1 



A variety with smaller vegetative cells and narrower, more elon- 

 gate gonidia. Cells 7-8yu, in diameter; heterocysts 7.5-10/x in diameter; 

 gonidia 9-10.5/* in diameter, 28-42/1, long. 



Euplankter. Wis. 



Anahaena Felisii ( Menegh. ) Bornet & Flahault 1888, p. 232 



PI. 116, Figs. 3, 4 

 Trichomes straight; solitary or in small clusters. Cells short- 

 cylindric, 6-7/* in diameter, 7-11/* long. Heterocysts ovate to sub- 

 cylindric, 7/* in diameter, 12-14/* long. Gonidia scattered; solitary 



[514] 



