prefer hard water habitats with a pH between 7.0 and 8.5 (S. crassa, 

 for example). Others are always found in shallow water which is 

 rich in organic acids and where there is a considerable amount of 

 disintegrating vegetation. 



As in most other genera of the Zygnemataceae, species identifica- 

 tion cannot be made without mature zygospores, or in some cases 

 aplanospores. Of the 258 or more known species of Spirogijra, only 

 5o have been found fruiting in our region, hence the following key 

 is greatly limited. 



In those species of Spirogijra which have a large number of closely 

 spiraled chloroplasts a count may be made easily by focusing on 

 a band at the upper side of the cell, counting this as 1. Then by 

 focusing down, the number of bands which are seen to be crossed 

 by this one and added to it will give the total number of chloroplasts. 



Key to the Species 



1. End walls of cells plane (not folded) 13 



1. End walls of cells replicate (infolded) — - -- -— -- — - - - 2 



2. Median wall of zygospore smooth 4 



2. Median wall of zygospore not smooth — 3 



3. Median spore wall with conical projections; 



spores 52-63m in diameter S. bonjsthenica 



3. Median spore wall reticulate; spores 45-75/li in diameter S. inconstans 



4. Conjugation tubes formed only from the male cells 5 



4. Conjugation tubes formed from both cells 6 



5. Zygospores ellipsoid; fertile cells inflated on both sides S. Spreeiana 



5. Zygospores ovate; fertile cells inflated on conjugating side S. Grevilleana 



6. Chloroplasts 1 (rarely 2) in each cell 8 



6. Chloroplasts 3-5 (2-4 in some cells) 7 



7. Vegetative cells 28-33/1 in diameter; zygospores 35-47/i 



in diameter; fertile cells cyhndric S. gratiana 



7. Vegetatixe cells 33-45/x in diameter; zygospores 45-60/i 



in diameter; fertile cells inflated S. fallax 



8. Vegetative cells 8-13-(15)m in diameter S. tenuissima 



8. Vegetative cells larger 9 



9. Vegetative cells 15-20At in diameter ( rarely with 2 



chloroplasts); fertile cells fusiform inflated S. inflate 



9. Vegetative cells larger 10 



10. Spores ovate 11 



10. Spores eUipsoid 1-* 



11. Inner layer of outer spore wall scrobiculate; vegetative cells 

 (28)-32-36-(44)ai in diameter; fertile cells cylindric S. protecta 



11. Both median and outer walls of spore smooth; vegetative cells 



19-30m in diameter; fertile cells slightly enlarged S. Weberi 



12. Fertile cells much inflated, fusiform; vegetative 



cells 24-30/x in diameter S. Farlotvii 



12. Fertile cells cyhndric; vegetative cells up to 40fi in diameter S. laxa 



13. Chloroplast 1 (rarely 2) in each cell 14 



13. Chloroplasts 2-16 in each cell - 38 



[ 308 ] 



