THE GREEN ALGAE OP NORTH AMERICA 9 



14. Z. ERICETORUM (Kiitz.) Hansgirg, 1886, p. 155 ; Zygo- 

 gonium ericetorum Collins, 1909, p. 120, with description. Re- 

 cent investigations have shown that the distinction between 

 Zygncma and Zygogonium cannot be maintained. Var. TER- 

 RESTRE becomes ZYGNEMA ERICETORUM var. TERRESTRE 

 Kirchner, 1878, p. 127. 



Page 105, for Key to the Species of Spirogyra, substitute, 

 i. Cell conjugating directly, not by a tube. 2. 



i. Cell emitting a tube. 4. 



2. Filaments 38-54 M diam., spore up to 60 /x. 58. S. stictica. 



2. Filaments 56-85 M diam., spore 75-115 M. 3- 



3. Fertile cells much inflated, up to 135 M- 55- S. florid ana. 



3. Fertile cells only slightly inflated. 54. S. illinoiscnsis. 



4. Dissepiments plane. 5. 



4. Dissepiments largely'replicate. 48. 



5. Chrotnatophore mostly single. 6. 



5. Chromatophores two or more. 27. 



6. Spore membrane punctate. 7. 



6. Spore membrane smooth. .11. 



7. Fertile cells not distinctly swollen. 41. S. daedalea. 



7. Fertile cells distinctly swollen. 8. 



8. Conjugating tube from both cells. 5. S.variansv&r.scrobictilata. 



8. Conjugating tube always or usually from male cell. 9. 



9. Fertile cells inflated on tube side only. 56. 5". micropunctata. 



9. Fertile cells inflated on both sides. 10. 



10. Spore about 36 M diam. 27. S. punctata. 



10. Spore 40-48 p. diam. 50. S. punctifornris. 



ii. Fertile cells not distinctly swollen. 12. 



ii. Fertile cells distinctly swollen. 17. 



12. Cells less than 30 M diam. 13. 



12. Cells 30 fj. diam. or more. 15. 



13. Spore ovoid, slightly longer than the diam. ; cells 22-25 M diam. 



9. 5. subsalsa. 

 13. Spore ellipsoid, 2-3 times longer than the diam. . 14. 



14. Chromatophore slender, with inconspicuous pyrenoids. 



7. S. communis. 



14. Chromatophore broad. i. S. longata. 



14. Chromatophore slender, with many large, distinct pyrenoids. 



3. S. Juergensii. 



15. Cells 30-48 fM diam. 16. 



15. Cells 48-70 M diam. 8. S. condensata. 



16. Cells seldom reaching 35 /u diam. ; chrouiatophore slender. 



38a. S. Lagerheimii. 



16. Cells 40-48 n diam. ; Chromatophore broad, dentate. 



2. S. porticdlis. 



