5. Median spore wall coarsely punctate, 33— 36ja in 



diameter Z. synadelphum 



5. Median spore wall finely punctate; 



spore 23— 26/x in diameter Z. carinatum 



6. Spores formed mostly within the conjugating tube 9 



6. Spores formed in one of the gametangia 7 



7. Vegetative cells 20-24/x in diameter; gametangia 



inflated and shortened; spore wall smooth .... Z. leiospermum 



7. Vegetative cells larger in diameter; gametangia 



cylindrical or inflated only on one side 8 



8. Median wall of zygospore smooth Z. insigne 



8. Median spore wall scrobiculate Z. stellinum 



9. Vegetative cells 24-40/x in diameter 10 



9. Vegetative cells 14-20^ in diameter 11 



10. Vegetative cells 30— 40^ in diameter; spores 35-50/li in diameter, 



wall with pits 2-3/u in diameter Z. pectinatum 



10. Vegetative cells 24-33^4 in diameter; spores 24-32;U in diameter, 



wall with pits less than 2/u, in diameter ... Z. conspicuum 



11. Median spore wall minutely punctate Z. micropunctatum 



11. Median spore wall scrobiculate Z. decussatum 



Zygnema carinatum Taft in Transeau, Tiffany, Taft, 



and Li 1934, p. 210 



PL 78, Fig. 11 



Vegetative cells 16-18|U, in diameter, 33-36/x long; fertile cells not 

 inflated. Zygospores formed in the tube; compressed-globose, ovate, 

 or top-shaped, compressed at right angles to the tube; median spore 

 wall blue and punctate, with a conspicuous transverse suture; 23-26ju, 

 in diameter, 29-33/a long. Sporangium finally encased in a thick 

 pectic layer. 



Mich. 



Zygnema chalybeospermum Hansgirg 1892, p. 243 



PI. 74, Fig. 2 



Vegetative cells 24-27/^ in diameter and up to 3 times the diameter 

 in length; fertile cells cylindrical (shortened). Zygospores formed 

 in one of the gametangia; globose or broadly ovate; median wall 

 blue and smooth; 30-35/x in diameter, 30-38/1, long. 



Mich. 



Zygnema conspicuum (Hass.) Transeau 1934, p. 208 



Vegetative cells (18)-22-27-(33);u in diameter, 50-90- (100)/. long; 

 fertile cells not inflated. Zygospores formed in the tube; globose or 

 ovate; median wall brown and rather coarsely pitted, the pits 1.5-2/* 

 in diameter; the spores 24-32/* in diameter, 26-33/. long. 



Mich. 



[324] 



