232 ZYGNEMATACEAE 



Usually the mature spores are ellipsoid, although ovoid spores 

 occur in most collections. The median wall may be smooth or 

 variously ornamented, and the color varies from pale yellow to 

 brown and black. 



Twelve species are here described. 



Key to the Species of SIROGONIUM 



I. Zygospores with a smooth median wall 2 



I. Zygospores with a variously ornamented median wall 4 



I. Zygospore lenticular 12. S. p/iacosponim 



2. Diameter vegetative cells usually less 



than 36 /J. 1. S. tenuius 



2. Diameter vegetative cells usually between 36 and 56/^ 3 



2. Diameter vegetative cells about 56- 



66 /i 4. S. fiuridamnn 



3. Diameter zygospores about 10-15 m 



larger than vegetative cells 2. ^S. sticticiitn 



3. Diameter zygospores 20-30 /a larger 



than vegetative cells 3. 6\ megasporum 



4. Median wall of zygospore single 5 



4. Median wall of zygospore double... 10. S./iiti 



5. Median spore wall "punctate" 6. 5. ceylaniciim 



5. Median spore wall finely corrugate and 



granulose 5. »S. pseiidofloridanum 



5. Median spore wall brown to black, verrucose 6 



5. Median spore wall reticulate g. 5. illinoicnse 



5. Median spore wall scrobiculate \\. S. indicum 



6, Diameter vegetative cells 65^2 /i. ... 7. ^S". ventersicujii 



6. Diameter vegetative cells 70-90/i.... S. S.melanospunijyj 



Descriptions or Species 



I. SiROCONiUM TENUIUS (Nordstcdt) Transeau 1934. Ohio Jour. 



Sci. 34, p. 420. Nordstedt. Bot. Notiser 1882. p. 47 (as 



Spirogyra stictica var. tetiuior). 



Vegetative cells 32-36^1 x 50-135 ;n; 2 to 5 chromatophores, nearly 



straight; conjugation direct between shortened and more or less rcflexed 



gametangia, separated by vegetative cells; receptive gamctangia intlatcd 



to 60/i; zygospores ellipsoid varying to ovoid, 47-50 /t x 60-S8/1; median 



spore wall yellow, smooth. 



United States: Oklahoma; Texas; Arkansas; Florida. 

 Argentina, Cordoba; Brazil, Mate (irosso; Burma. 



