5. Trichomes not tapering to a hair; short, abruptly ending C. atricha 



5. Trichomes decidedly tapering, sometimes to a long hair 6 



6. Filaments associated to form a colonial expanse C. parietana 



6. Filaments solitary, or few together, scattered or epiphytic 7 



7. Cells very short, %-% as long as wide; sheath brown C. breviarticulata 



7. Cells longer; sheath colorless ..__ 8 



8. Trichomes slender, 3.5-4^ in diameter at the base; filaments 



5-7/x in diameter C. epiphytica 



8. Trichomes stouter, 12/^ in diameter at the base; filaments 



18-24fi in diameter C. adscendens 



Calothrix adscendens ( Naeg. ) Bornet & Flahault 1886, p. 365 



PL 130, Figs. 9-11 

 Filaments solitary or in small clusters, tapering from the base to 

 apex, sheath wide, lamellated; heterocysts basal, 11^ in diameter, 

 11.8/x long; vegetative cells 9.2/^ in diameter, 7.4-8/j. long at the base; 

 filament 12-18- ( 24 )/x wide at base. 



Attached to larger filamentous algae and other aquatic plants. Wis. 



Calothrix atricha Fremy 1930, p. 261 

 PI. 129, Fig. 6 



Trichomes short, solitary or in clusters of 3-4, curved and torulose, 

 sheaths thin, colorless, not lamellated, slightly tapering to a blunt 

 apical cell; heterocysts basal, usually in pairs, spherical, d/x in 

 diameter; vegetative cells 7.4-8;^ in diameter at the base, 1-1 1/2 

 times as long as wide. 



Our plants are questionably assigned to this species originally 

 described from Africa. The torulose character of the filaments and 

 the shape of the cells, together with the characteristics of the sheath 

 and the form of the apical region of the trichome, agree with the 

 description. 



Wis. 



Calothrix Braunii Bornet & Flahault 1886, p. 368 

 PI. 131, Fig. 12 

 Trichomes parallel, gradually tapering to a point, compactly 

 arranged to form a colonial expanse on submerged substi^ates; 

 sheath thin and colorless; heterocysts hemispherical, basal; vegeta- 

 tive cells shorter than broad or about as long, constiicted at the 

 cross walls, 6-7/i, in diameter at the base. 



On submerged vegetation and stones in hard water lakes. Wis. 



Calothrix breviarticulata West & West 1897, p. 240 

 PI. 132, Fig. 1 

 Filaments mostly solitary, tapering gradually from a broad base 



[552] 



