154 ZYGNEMATACEAE 



nation of dimensions, unilaterally inflated sporiferous cells, and the inflated 

 sterile cells. Has been found hybridizing with S. porttcalts, S. longata, and 

 S. communis and producing a variety of segregates. Due to the occurrence 

 of haploid segregates and the wide overlapping of cell and spore dimensions, 

 it has not been found advisable to separate the variants further. 



13. Spirogyra bicalyptrata Czurda 1930. Beih. Bot. Zentralbl. 



47, p. 31. 



Vegetative cells 36-59^1 x 60-110/^, with plane end walls; chro- 

 matophore i (rarely 2); conjugation scalariform; tubes formed by both 

 gametangia; fertile cells swollen on the conjugating side; zygospores 

 ellipsoid, 31-34/^ x 55-70 m; median spore wall brown, smooth, with 

 dark brown polar thickenings. (Pi. XXII, Fig. 2.) 



Czechoslovakia; Austria; Greece. 



Distinguished from S. varians by the occurrence of 2 chromatophores 

 in some cells and the brown polar thickening of the median wall. A similar 

 local polar thickening sometimes occurs in scattered spores of other species. 



14. Spirogyra circumlineata Transeau 1914. Amer. Jour. Bot. 



l,p.293. 

 Vegetative cells ( ^58-) 40-48 /x x 1 20-240 /m, with plane end walls; 

 I chromatophore, slender, making 4 to 8 turns; conjugation scalariform; 

 tubes formed by both gametangia; fertile cells inflated on the conju- 

 gating side only; zygospores ellipsoid, 40-50 m x 70-125 /x; median spore 

 wall yellow-brown, smooth; suture more or less prominent. (PI. XXII, 



Fig- 3-) 



United States: Iowa; Illinois; Michigan; Ohio. 



Distinguished from S. varians by the larger dimensions, the slender 

 chromatophore making a larger number of turns, the distinct suture encir- 

 cling the spore, and the absence of inflated sterile cells. 



15. Spirogyra supervarians Transeau 1934. Trans. Amer. Micros. 



Soc. 53, p. 208. 



Vegetative cells 50-57 /j. x 50-1 44 m; i chromatophore; cells with 

 plane end walls; conjugation scalariform; tubes formed by both gam- 

 etangia; receptive gametangium inflated on the inner side; zygospores 

 ellipsoid, small in proportion to the gametangia, 35-40 m x 54-74 m; 

 median spore wall smooth, yellow. (PI. XXII, Fig. 7.) 



Africa, Cape Flats (E. Stephens Coll.). 



Similar to S. varians in appearance, but wiih much larger dimensions 

 throughout, and without inflated sterile cells. 



16. Spirogyra fennica Ccdercreutz 1924. Acta Soc. pro Fauna et 



Flora Fennica. 55 (2), p. 4. 

 Vegetative cells 15-19M x 60-260^, with plane end walls; i chro- 



