Schroederia Judayi G. M. Smith 1916, p. 474 

 PL 57, Figs. 5, 6 



Cells fusiform, straight or arcuate, the poles narrowed and ex- 

 tended into long setae, one of which terminates in short bifurcations; 

 1 chloroplast, with a single pyrenoid; cells 2.5-6/a in diameter, 

 45-63/A long, including the setae, which are 10-16/x long. 



This species resembles an unattached Characium and should be 

 compared with some of the species of that genus. 



Rare; in euplankton. Mich., Wis. 



Schroederia setigera (Schroed. ) Lemmermann 1898c, p. 311 



PI. 57, Fig. 4 



Cells fusiform, mostly acicular, the poles extended into long, 

 fine setae, one of which is bifurcate near the tip, forming recurved 

 bristles; chloroplast plate-like, covering most of the cell wall, 

 usually with 1 pyrenoid; cells 3-6/i, in diameter, 60-85^ lo^^g' ^^- 

 cluding the setae, which are 13-17/i, long. 



In plankton of lakes. Wis. 



SELENASTRUM Reinsch 1867, p. 64 



A colony of 4—16 lunate or sickle-shaped cells with acute apices, 

 the dorsal or convex walls adjacent; not inclosed by a gelatinous 

 envelope; chloroplast 1, parietal, lying along the convex wall, 

 usually with 1 pyrenoid. 



Species of this genus should be compared with Kirchneriella 

 which has somewhat scattered lunate cells within a gelatinous 

 envelope. 



Key to the Species 



1. Cells decidedly sickle-shaped, 19-28^ from tip to tip S. gracile 



1. Cells lunate (crescent-shaped), or arcuate but not 



sickle-shaped, mostly smaller 2 



2. Cells arcuate, 1.2-2.5/^ in diameter S. Westii 



2. Cells lunate, larger in diameter.. 3 



3. Cells 5— 8m in diameter, 16— 42/x from tip to tip S. Bibraianum 



3. Cells (2)-3|ti in diameter, l-d/j. from tip to tip ..S. minutum 



Selenastrum Bibraianum Reinsch 1867, p. 64 



PI. 57, Fig. 9 



Colony ovate in outline, composed of 4-16 lunate or sickle-shaped 



cells with sharp apices and arranged so that the convex surfaces 



are apposed and directed toward the center of the colony; cells 



5-8/A in diameter, 20-38/* long; distance between apices 16--42ju. 



Rare; in several lakes, mostly soft water, and in acid swamps. 

 Mich., Wis. 



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