Cylindrospermum minutissimum Collins 1896, p. 120 



PL 131, Fig. 13 

 Filaments loosely entangled, forming a thin blue-green skein. 

 Vegetative cells quadrate-cylindric; not constricted at the cross 

 walls; 2-2.5)u in diameter, 4-5ja long. Heterocysts elongate, Afx. in 

 diameter, 6-8/^ long. Gonidia solitary or in pairs; ellipsoid; the wall 

 smooth; 8-9/i in diameter, 18-20/x long. 



On mats of algae in shallow water; tychoplankter. Wis. 



Cylindrospermum minutum Wood 1874, p. 39 

 Filaments much entangled in a mucilaginous expanse; forming 

 bright blue-green to dark green patches on submerged aquatics; 

 frequently scattered in minute clusters among other algae. Cells 

 short-cylindric or slightly swollen, with constrictions at the cross 

 walls; S-Afi in diameter, 3.5-4.8pi long. Heterocysts ovate or sub- 

 globose, 5-7/A in diameter, 7-8/x long; hirsute, with long radiating 

 gelatinous fibrils. Gonidia ovate, 6-7/i, in diameter, 16-19/x long, 

 with a punctate or granular wall. 



Common in several acid or soft water lakes and small ponds. 

 Mich., Wis. 



Cylindrospermum muscicola Kuetzing 1845, p. 173 

 PL 122, Fig. 16 



Filaments entangled in a mucous expanse, forming dark green 

 patches on submerged aquatics {Potamogeton, Elodea, Ceratophy- 

 llum). Cells quadrate to cylindric; with slight constrictions at the 

 cross walls; 3.5-5.5/a in diameter, 4-6.5/^ long. Gonidia broadly ovate; 

 with thick, smooth wall; 9-12/x in diameter, (9)-16-20/i long. 



A rather common species, occurring mostly in hardwater habitats, 

 alkaline swamps, and shallow lakes. The broadly ovate gonidia are 

 characteristic. Mich., Wis. 



Cylindrospermum stagnale ( Kuetz. ) Bornet & Flahault 1888, p. 250 



PL 122, Figs. 17, 18 



Filaments entangled or parallel in a mucilaginous expanse, at- 

 tached or floating. Trichomes with cells constricted at the cross 

 walls. Cells slightly swollen, 3.8-4.5-(6)/x in diameter, 7-13.4/x long. 

 Heterocysts globular or elongate, 6-7)U, in diameter, 7-16//, long. 

 Gonidia ovate or subcyhndric; with thick, smooth wall, (8)-10- 

 15-(16)/t in diameter, 19-21.6- ( 40 )/t long. 



This is the most common species of the genus in our collections. 

 It is found on or among aquatic vegetation such as submerged 

 mosses, and in shallow water on dead and decaying grasses and 



[531] 



