THE GREEN ALGAE OF NORTH AMERICA 143 



a formless mass. Until more is known of its history, it cannot 

 be properly located. 



KEY TO THE GENERA OF PROTOCOCCACEAE. 



i. Cells attached at base or with basal prolongation. 2. 



i. Cells without basal attachment or prolongation. 3. 



2. Fresh water ; chromatophore cup-shaped ; one pyrenoid. 



6. CHARACIUM. 



2. Marine; chromatophore more or less broken ; several pyrenoids. 



7. CODIOL,UM. 



3. Endophytic. 4. 



3. Not endophytic. 5. 



4. Color more or less deep red. 4. RHODOCHYTRIUM. 



4. Color green. 6. 



5. Cell membrane with spines, ridges, or other projections. 



2. TROCHISCIA. 



5. Cell membrane smooth. i. CHI.OROCOCCUM. 



6. Zoospores and gametes biciliate. 3. CHI,OROCHYTRIUM. 



6. Zoospores 4-ciliate ; gametes unknown. 5. CHLOROCYSTIS. 



i. CHLOROCOCCUM Fries, 1825, p. 356. 



Cells spherical with usually thin membrane ; chromatophore 

 covering nearly the whole cell wall, with one pyrenoid ; asexual 

 reproduction by biciliate zoospores, produced many in a cell. 



The species of this genus are found in fresh water, and more 

 especially in wet places on land, often where there are impuri- 

 ties from sewage or other animal matter that would be fatal to 

 most green algae. It is extremely hard to draw a line between 

 Chlorococcum and Gloeocystis on the one hand and Zoochlorella on 



the other. 



KEY' TO THE SPECIES OF CHLOROCOCCUM. 



i. Endozoic. 3. C. endozoicum. 



i. Not endozoic. 2. 



2. Forming thin coatings in moist places. i. C. huwicola. 



2. Forming gelatinous submerged masses. 2. C. infusionum. 



1. C. HUMICOLA (Nag.) Rabenhorst, 1868, p. 58 ; P. B.-A., 

 No. 1066; Cystococcus humitola Niigeli, 1848, p. 85, PI. III.E. 

 Cells varying much in size, 3-25 p. diam., spherical, solitary or 

 united by 2-4; membrane thin, uniform, hyaline. Fig. 31. 

 Greenland, Mass., R. I. Europe. 



Forming thin green coatings in moist places, especially under 

 dripping water. 



2. C. INFUSIONUM (Sclirank) Meneghini, 1846, p. 27, PI. 

 II, fig. 3; P. B.-A., No. 1 1 19. Cells spherical, 15-45 



