from the male gametangia only; fertile cells grouped, in series of 2-4. 

 Zygospores ellipsoid; median spore wall smooth and yellow-brown; 

 44-54^ in diameter, 90-150/* long. 

 Mich. 



Spirogyra rhizobrachialis Jao 1936a, p. 57 

 PL 76, Figs. 1, 2 



Filaments of rather stout cells (40)-45-59/x in diameter, 114-240/x 

 long, with plane end walls; chloroplasts 3-5, crenate and deeply 

 toothed on the margins, making li^ to 2i^ turns. Conjugation by 

 tubes from both gametangia; fertile cells cylindric, sterile cells fre- 

 quently forming tubes which develop highly branched rhizoidal 

 processes at their ends. Zygospores ellipsoid; median spore wall 

 irregularly and coarsely reticulate, brown; (38)-40-62/x in diameter, 

 lllju long. 



Our specimens agree closely with this species in habit of growth 

 and spore characters, but vary in dimensions from the original 

 description. 



Bright green cottony masses in soft water lakes. Wis. 



Spirogyra rivularis ( Hass. ) Rabenhorst 1868, p. 243 



Vegetative cells 36-41/x in diameter, 100-400/i, long, with plane end 

 walls; chloroplasts 2-3, making 2i/2 to 314 turns. Conjugation by 

 tubes from both gametangia; fertile cells cylindric. Zygospores ellip- 

 soid or cylindric-ellipsoid; median spore wall smooth. 



Mich. 



Spirogyra scrohiculata ( Stock. ) Czurda 1932, p. 182 

 PI. 76, Figs. 3, 4 



Filaments of short cells, 30-34-^ ( 40 )/x in diameter, (30)-90-136/t 

 long, with plane end walls; chloroplast solitary, making 1 to 5 turns. 

 Conjugation by tubes from both gametangia, the fertile cells inflated 

 on the conjugating side; zygospores ellipsoid, median spore wall 

 deeply pitted and brown; 33-35-(38)/a in diameter, 44-50-(68)/x long. 



Among other algae in swamps. Mich., Wis. 



Spirogyra singularis Nordstedt 1880, p. 23 



Vegetative cells 29-39/* in diameter, with plane end walls; chloro- 

 plast solitary. Conjugation by tubes from both gametangia; fertile 

 cells cylindric. Zygospores ellipsoid or cylindric-ellipsoid, not later- 

 ally compressed; median spore wall smooth; 27-37/* in diameter. 



Mich. 



[ 320 ] 



