WISCONSIN PHYTOPLANKTON 59 



drical, with rounded ends. Spore wall delicate, smooth, and hyaline. 

 (Facultative planktont). 



Cells 5-7 fj, broad, 5-9.5 p. long; heterocysts 8-9.5 /* broad, 8-14 ^ 

 long ; spores 9.5-12 /x broad, 40-70 /* long. 



Bone (ss), Center (cc). 



ANABAENA SPIROIDES var. CRASSA Lemmermann. PI. 9, Figs. 1-3. 



Bot. Cent. 76: 155. 1898; Kryptogamenfl. d. Mark. Brandenburg 3, Algen'l: 

 188, 159, figs. 15-16. 1907. 



Filaments solitary, free-floating; forming a regular, evenly spaced 

 spiral enclosed by a very transparent, homogeneous, gelatinous envelope. 

 Cells spherical or with flattened ends. Heterocysts spherical, hyaline 

 or pale yellow. Spores solitary, remote from the heterocysts, generally 

 broadly ovoid. Cell contents rarely homogeneous, usually with numer- 

 ous pseudovacuoles. (Euplanktont). 



Cells 11-15 fj. broad ; heterocysts 10-17 p broad ; spores 20-25 ^ broad, 

 27-42 (generally 27-31) /x long. Spirals 50-60 p. broad and 45-55 /* 

 between turns. 



Big Butternut (cc), Big St. Germain (cc), Granite (cc), Hooker (c), Ke- 

 gonsa (a), Long (2) (sss), Little Butternut (cc), Mendota (cc), Monona (aa), 

 North Twin (sss), Round (3) (ss), South Turtle (c), Vermilion (ccc). 



ANABAENA CIRCINALJS (Kutzing)Rabenhorst. PI. 9, Figs. 4-5. 



Algen No. 209. 1852; Phillips, Grevillea 9: 5, pi. 134, figs. e-g. 1880; Bornet 

 et Flahault, Ann. Sci. Nat. 7 Ser. Bot. 7: 230. 1888. 



Anabaena Hassallii (Kiitzing) Wittrock. Bot. Not. 1882: 58. 1882. 



Filaments free-floating, rarely solitary, curved or sigmoid; usually 

 greatly and irregularly twisted to form floccose masses. Filaments 

 with or without a copious, hyaline, gelatinous envelope. Cells spheri- 

 cal or appreciably flattened at the poles, generally with numerous 

 pseudovacuoles. Heterocysts spherical to subspherical. Spores usu- 

 ally remote from the heterocysts, cylindrical, with rounded ends when 

 mature, frequently curved and with smooth walls. (Euplanktont). 



Cells 8-14 fi broad; heterocysts 8-10 /* broad; spores 16-18 p. broad, 

 26-30 /j. long when mature. 



Center (ss), Chain (sss), Lac la Belle (rr), Mercer (rr), Nagawicka (rr), 

 Pike (r), Upper Nashotah (rr), Wapagossett (sss), Winnebago (ss). 



This species differs from A. flos-aquae in the loose looping of the 

 trichomes, the larger vegetative cells and the broader spores. 



