THE GREEN ALGAE OF NORTH AMERICA 333 



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



4. Some cells ovoid or pyriforin. 5. 



5. Cells 40-70, rarely 100 M diani. 40. C. amphibia. 



5. Cells 120-250 fj. diatii. 39. C. trichotoma. 



6. Main filaments from 150 M up. 7. 



6. Main filaments seldom reaching 150 /u. lo. 



7. Lower cells 10 diam. long or more. 8. 



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



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



34. (7. graminea. 



8. Several cells usually between successive branchings. 9. 



9. Branching alternate or opposite, except near the base. 



33. C. catenifera. 

 9. Branching generally dichotomous throughout. 35. (". prolifera. 



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



12. C. constricta. 



10. Cells without regular constrictions. 20. 



ii. Ramuli curved. 25. C. microcladioides. 



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. fascicularis. 

 13. Ramuli short, stout, with constricted nodes. 



28. C. Hut chin siae. 



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



36. C. fuliginosa. 



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



15. Filaments cylindrical. 2?. 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 ramuli very short, often of a single cell; cells in ramuli 



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



17. Ultimate ramuli not extremely short. 18. 



j8. Branching patent, except at the extreme base. 



15. C. crucigera. 



18. Branching generally erect. 19. 



19. Ramuli not exceeding 60 fj. diani. 30. C. ovoidea. 



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



20. Main filaments distinctly angled or flexuous. 21. 



20. Main filaments straight or nearly so. 34. 



21. Ramuli in clusters at tips. 22. 



21. Rainuli not distinctly clustered. 23. 



