THE GREEN ALGAE OP NORTH AMERICA 333 



4. Cells cylindrical throughout. 37. C. Magdalenae. 



4. Some cells ovoid or pyriform. 5. 



5. Cells 40-70, rarely 100 ,u diam. 40. C. amphibia. 



5. Cells 120-250 ,u diatn. 39. C. trichotoina. 



6. Main filaments from 150 fj. up. 7. 



6. Main filaments seldom reaching 150 M- 10. 



7. I^ower cells 10 diatri. long or more. 8. 



7. Lower cells less than 10 diam. long. u. 



8. Di- or polychotoruous branching normally from every cell. 



31. C. graininea. 



8. {Several cells usually between successive branchings. 9. 



9. Branching alternate or opposite, except ne"ar the base. 



33. C. cat en if era. 

 9. Branching generally dichotomous throughout. 35. C. prolifera. 



10. Cells generally with a sharp constriction near the base. 



12. C. constricta. 



10. Cells without regular constrictions. 20. 



u. Ramuli curved. 25. C. tnicrocladioides. 



ii. Ramuli straight or nearly so. 12. 



12. Ramuli clustered. 13. 



12. Ramuli not clustered. 14. 



13. Ramuli long, slender, cylindrical or nearly so. 



26. C. fascii'itlaris. 

 13. Rarnuli short, stout, with constricted nodes. 



28. C. Hutc/iinsiae. 



14. Diameter nearly the same in all parts of the frond. 



36. C. fnlig'inosa. 



14. Terminal divisions markedly smaller than main stems. 15. 



15. Filaments cylindrical. 22. C. hirta. 



15. Nodes more or less constricted. 16. 



16. Cells about the same length in proportion to the diameter in all 

 parts of the frond. 32. C. catenata. 



16. Upper cells proportionally shorter than the lower. 17. 



17. Ultimate rarnuli very short, often of a single cell; cells in rarnuli 



ovoid, 1-2 diam. long. 18. C. brachyclona. 



17. Ultimate ramuli not extremely short. 18. 



18. Branching patent, except at the extreme base. 



15. C. crucigcra. 



18. Branching generally erect. 19. 



19. Ramuli not exceeding 60 /.i diam. 30. C. oroidea. 



19. Ramuli 70-100 ju diam. 31. C. utriculosa. 



20. Main filaments distinctly angled or flexuous. 21. 



20. Main filaments straight or nearly so. 34. 



2i. Ramuli in clusters at tips. 22. 



21. Ramuli not distinctly clustered. 23. 



