shortened, the receiving cell becoming somewhat swollen. Zygo- 

 spores ovate; median spore wall reticulate and brown; 43-46/x in 

 diameter, 52-62/a long. 

 Wis. 



Spirogyra tenuissima ( Hass. ) Kuetzing 1849, p. 437 



Vegetative cells (8)-9-12-(15)/i, in diameter, 4-12 times the diam- 

 eter in length with replicate end walls; chloroplast solitary, making 3 

 to 51/2 turns. Conjugation by tubes from both gametangia; fertile 

 cells fusiform, inflated. Zygospores ellipsoid; median spore wall 

 smooth and yellowish; 30/a in diameter. 



Mich. 



Spirogyra Teodoresci Transeau 1934a, p. 420 



Vegetative cells 23-30/;. in diameter, 42-90/t long, with plane end 

 walls; chloroplast solitary, making 1 to 5 turns. Conjugation by tubes 

 from both gametangia; fertile cells greatly inflated on the conjugat- 

 ing side. Zygospores ellipsoid, varying to ovate or globose; median 

 spore wall smooth; 26-33/a in diameter, 45-55|a long. 



Mich. 



Spirogyra triplicata ( Collins ) Transeau 1944, p. 243 



Vegetative cells 34-40 ( 48 )/t in diameter, 2-4 times the diameter 

 in length, with plane end walls; chloroplasts 3, making 1 to 2 turns. 

 Conjugation by tubes from both gametangia; fertile cells cylindric. 

 Zygospores ovate to subglobose, not compressed; median spore wall 

 smoQth; 34-48/i, in diameter, 48-54/a long. 



Mich. 



Spirogyra varians ( Hass. ) Kuetzing 1849, p. 439 

 PI. 76, Figs. 11, 12 



Filaments of short cells, (28)-33-(40)/t in diameter, 51-85-(120)iLt 

 long, with plane end walls; chloroplast solitary, making 1/0 to 4 turns. 

 Conjugation by tubes from both gametangia; fertile cells inflated on 

 the conjugation side only. Zygospores ellipsoid or ovate-ellipsoid; 

 median spore wall smooth; 32-40/t in diameter, 50-63- ( 100 )/^ long. 



Mich. 



Spirogyra Weberi Kuetzing 1843, p. 279 

 PI. 76, Figs. 8-10 

 Filaments of long cells, 19-30/x in diameter, 80-480ja long, with 

 replicate end walls; chloroplast solitary, broad, making 3 to 61/2 turns. 

 Conjugation by tubes from both gametangia; fertile cells cylindric. 

 Zygospores cylindric-ovate; median spore wall smooth and brown; 

 2i-25/x in diameter, 30-95/t long. 



This species has never been found in pure growth; it seems always 



[322] 



