ANAB^NA. 287 



from mutual pressure transversely elliptic or quadrate ; 

 heterocysts intercalated, elliptical ; spores globose. 



Diameter of filaments, 4-6 ^ ; heterocysts often twice the 

 size ; spores, 8-10 ju. 



Syu. Nostoejlos-ciquce, Lyngb. ; A. gelatinosa, Wood. 



Yar. CIROINALIS, (Bab. ) Kirch. 



Trichomes more circinate and joints larger; spores and 

 heterocysts not proportionately so much larger than the 

 typical form ; sometimes very little larger than the cells. 



Diameter, 7-10 yu. 



Syn. Anabcwia circinalis, Eab. ; A. spiralis, Thompson ; Tri- 

 chormns spiralis, Balfs. 



Plate CXCVIII, figs. 20-23, filaments of type-form ; figs. 

 24-26, var. circinales, from specimens from Minnesota, and 

 from Chautauqua Lake, N. Y. 



Yar. AESTUARII, Wolle. 



Same in size as circinales, but filaments not so circinate, 

 and heterocysts and spores very slightly larger than the 

 cells. 



Plate CXCY1II, figs. 9, 10, specimens collected at Dennis - 

 ville, New Jersey. See note under generic description. 



GIGANTEA, Wood. 



Filaments occur floating singly or in great numbers, 

 straight, but in the young state often spirally convolute; 

 articles mostly subgiobose, closely connected, granular ; 

 heterocysts subspherical, intercalated, a very little larger 

 than the vegetative cells, thickened at each end in a puncti- 

 form manner ; spore subspherical. 



Diameter of vegetative cells, 9-11 //; heterocysts, 12 >. 



Found occasionally intermingled with Bother algse, or 

 forming a part of a thick, dirty green, almost pulverulent 

 scum. 



Plate CXCYIII, figs. 27, 28, two short filaments ; one in 

 process of cell division. 



ANABJENA VAEIABILIS, Kg. 



Gelatinous, submembranaceous, deep blue green ; tri- 

 chomes slightly flexuously curved, almost parallel, verdigris 

 green ; joints globose or elliptic, compressed or depressedly 



subcylindrical, equal to one-half longer than broad ; hetero- 

 19 



