THE GREEN ALGAE OF NORTH AMERICA 277 



17. Setae articulate. 18. ARTHROCHAETE. 



17. Setae inarticulate. 17. CHAETOBOLUS. 



18. Cells solitary. i. DIPLOCHAETK. 



18. Cells united in filaments. 19. 



19. Epiphytic or in loose tissue of other algae. 20. 



19. Living in the membrane of other algae or in outer coating of mol- 

 lusks. 24. 



20. Fresh water. 4. CHAETOSPHAERIDU-M. 



20. Marine. 21. 



21. Setae present. 22. 



21. No setae. 23. 



22. Setae arising from the ends of upright cells. 5. ACROCHAETE. 



22. Setae arising from small special cells. 8. BoLBOcoivEON. 



23. Basal network with short vertical branches. 7. PSEUDOPICTYON. 

 23. Branching irregular, no definite network. 6. ENDOPHYTON. 



24. In cell wall of algae. 2. ENDODERMA. 



24. In outer coating of mollusk shells. 3. TELLAMIA. 



In addition to the genera given in the foregoing key, there 

 are a few others which may be reduced or rudimentary forms 

 belonging to this family ; the cells have the same structure, 

 some species at least produce zoospores and aplanospores, and 

 all have regular vegetative cell-division ; there seems to be no 

 better place for them, 

 i. Cells in older plants borne on stalks formed from the cell wall. 



27. UROCOCCUS. 

 i. Cells never stalked. 2. 



2. Cells dividing and soon separating, or forming small irregular 

 masses or short filaments. 26. PLEUROCOCCUS. 



2. Cell wall persisting and enclosing walls of later generations. 3. 

 3. Division in one direction. 28. DACTYLOTHECE. 



3. Division in two or three directions. 4. 



4. Families encircled by one or more opaque bands. 



31. GLOEOTAENIUM. 

 4. No opaque bands. 5. 



5. Families spherical or irregular. 6. 



5. Families united into subcylindrical, branching thalli. 



32. PALMODICTYON. 

 6. Families enclosed in a spherical, gelatinous envelop. 



30. GLOIOCOCCUS. 

 6. Families with no general envelop. 29. GLOEOCYSTIS. 



i. DIPLOCHAETE Collins, 1901, p. 242. 



Cells solitary or a few united into a gelatinous, subfilamen- 

 tous series, globose, flattened, ellipsoid or ovoid, furnished with 



