proportions, dark green in color. Cells short cylindric; constricted at 

 the cross walls; 2.5-4.2/* in diameter, 4-5/x long. Heterocysts elon- 

 gate, 5— 6/i, in diameter, 7— 12/* long. Gonidia solitary, elongate- 

 ellipsoid to oblong; the wall thick and smooth; 12— 14/a in diameter, 

 20-38/t long. 



On submerged aquatic plants or on stones which are encrusted 

 with sediment. Mich., Wis. 



Cylindrospermum majus Kuetzing 1843, p. 212 

 PI. 122, Figs. 11, 12 



Filaments entangled to form dark green mucilaginous patches. 

 Cells short-cylindric; slightly swollen and constricted at the cross 

 walls; 3.7-5/i, in diameter, 4-6/x, long. Heterocysts elongate, little 

 larger than the vegetative cells, up to 10/x long. Gonidia ellipsoid 

 to subcylindric, with a roughened and punctate wall; 14.8/i in 

 diameter, 27 fx long, including the sheath. 



In several soft water and acid lakes and pools. Wis. 



Cylindrospermum Marchicum Lemmermann 1910, p. 196 



PL 122, Fig. 13 



Filaments entangled, forming small mucilaginous patches. Cells 

 short-cylindric; slightly constricted at the cross walls; 2.5-3.5/* in 

 diameter, 7.4-8.5/* long. Heterocysts ovate to subquadrate-ovate, 

 2.5-3/* in diameter, 3-4/* long. Gonidia ovate to subcylindric; in a 

 catenate series adjoining the heterocyst; with thick smooth walls; 

 4-5.5/* in diameter, (12)-14.8-16/i long. 



This plant should be compared with C. catenatum from which it 

 differs but very slightly, chiefly in size. It was originally described 

 as a variety of that species. 



On moist substrates and on vegetation in shallow water. Wis. 



Cylindrospermum minimum G. S. West 1914, p. 1016 

 PL 122, Figs. 14, 15 



Filaments solitary, or in small dusters, straight or gracefully 

 curved; cells rectangular to short cylindric, 1.8-2/* in diameter, 

 1.8-3.5/1 long; heterocysts subglobose to ellipsoid, 2/i in diameter, 

 2.5—2.7/* long; gonidia solitary subcyclindric, 3.5— 3.8/i in diameter, 

 8—9/* long, with a thick smooth wall. 



This species was originally described from high altitudes in the 

 Andes. Such a record naturally casts doubt on the assignment of 

 our specimens, but they agree so well with West's description that 

 the disposition seems justified. I have not seen the type specimens 

 for comparison. 



Rare in tychoplankton. Wis. 



[530] 



