SPIROGYRA 131 



II. Most of the spores less than 28 /a in thickness 12 



II. Most of the spores more than 28 ju, in thickness 13 



12. Diameter vegetative cells 11- 



14.5/1, sterile cells inflated or 



bullate 50. 5. porangabae 



12. Diameter vegetative cells 19-22 /x, 



sterile cells bullate 21. S. bullata 



12. Diameter vegetative cells 18-26 /i. i. S. communis 

 12. Diameter vegetative cells 25-29 /a 2. S.intorta 



13. Diameter vegetative cells 24-30/1, di- 

 ameter zygospores 28-3310. 3- ^^^ juergensii 



13. Diameter vegetative cells 29-39 /a, di- 

 ameter zygospores 27-36/1 4. .S. singularis 



13. Diameter vegetative cells 32-40 /a, di- 

 ameter zygospores 36-43 /a 5.5. silvicola 



14. Vegetative cells less than 30/1 in diameter 15 



14. Vegetative cells 30-40 /x in diameter 17 



14. Vegetative cells more than 40/1 in diameter 18 



15. Diameter vegetative cells 19-21 /a 18. S. gibberosa 



15. Diameter vegetative cells 16-24/1 8. 5. gracilis 



15. Diameter vegetative cells 23-30 /j. 16 



16. Fertile cells only slightly inflated 9. S. jragilis 

 16. Fertile cells strongly inflated 10, S.teodoresci 



17. Median spore wall smooth, outer scro- 



biculate 11. S. pseudovarians 



17. Median spore wall smooth, outer 



smooth 12, S. varians 



17. Median spore wall smooth, with dark 



brown polar caps 13- '5'. bicalyptrata 



18. Diameter vegetative cells 40-50 /a, 



diameter spores 40-50 /t 14. 5. circumlineata 



18. Diameter vegetative cells 50-57 /a, 



diameter spores 35-40 /a 15, 5. supervarians 



19. Vegetative cells less than 24/1 in diameter 20 



19. Vegetative cells more than 24 /a in diameter 21 



20. Chromatophore i, diameter veg- 

 etative cells 15-19/1, spore length 

 45-55 /A 16. 5. fennica 



20, Chromatophore 1-2, diameter 

 vegetative cells 17-20/1, sterile 

 cells bullate 22. S. pratensis 



