Oscillatoria limosa (Roth) C. A. Agardh 1812, p. 35 

 PI. 109, Fig. 17 



Trichomes usually forming a very dark blue-green or brownish 

 plant mass attached to submerged objects or forming fihns on sandy 

 bottoms, although rarely sohtary or loosely entangled among fila- 

 mentous algae; straight, tapering Httle or not at all toward the 

 apex. Apical cell rotund, the outer membrane thickened but without 

 a definite calyptra. Cells 12-18-(20)/-t in diameter, 3.7-5/x long, not 

 constricted at the cross walls, which are usually granular. Trichomes 

 not infrequently inclosed in a hormogonous sheath. 



Common in stagnant water of ditches and small ponds; tycho- 

 planktonic in lakes. Mich., Wis. 



Oscillatoria minima Gicklhorn 1921, p. 4 

 PI. 107, Fig. 24 

 Trichomes somewhat coiled and spirally twisted, golden-colored, 

 inclosed in a delicate mucilaginous sheath, not tapering toward the 

 apex; apical cell not capitate and without a calyptra; cells 2fi in 

 diameter, 5-6fjL long. 

 Mich. 



Oscillatoria nigra Vaucher 1803, p. 192 



PI. 109, Fig. 18 



Trichomes aggregated to form a thick, mucilaginous blackish- 

 green plant mass on submerged objects, becoming free-floating; 

 straight or slightly twisted and entangled, slightly tapering toward 

 the apex and curved (or straight). Apical cell rotund, not capitate 

 and without a calyptra. Cells 8-10/a in diameter, 3.7-4.5/x long; 

 sHghtly constricted at the cross walls, which are sometimes gran- 

 ular; cell contents dark olive-green. 



Common in the shallow water of many lakes and ponds. Mich., 



Wis. 



Oscillatoria ornata Kuetzing 1845-1849, p. 30 



Trichomes forming a dark, blue-green plant mass; spirally twisted 

 at the end, not at all or scarcely tapering toward the apex. Apical 

 cell broadly rounded, not capitate and without a calyptra. Cells 

 9-11^ in diameter, short, Vo-i/e times as long as broad (2-5/x long), 

 constricted at cross walls which are granular. 



Mich. 



Oscillatoria princeps Vaucher 1803, p. 190 



PI. 110, Fig. 1 

 Trichomes solitary or loosely entangled to form small floating 

 plant masses, which are black-green in color; individual plants 



[489] 



