28 GENERA OF ALG^. 



Q. Filaments 2 or more laterally united, or in flat narrow bands, 



Schizogonium, 26 



R. With one row of cells, (S). 



S. Without lateral processes (except Ulothrix rivularis), strictly un- 

 branched . . . . .... Ulothrix, 25; Conferva, 27 



S. With short, irregular, lateral processes, 1-3 or more celled, 



Rhizodonium, 29 

 T. Parasitic, i. e. penetrating the membrane of the host {g). 

 T. Not parasitic (*). 



* Cells united or clustered in families (U). 



* Cells scattered, independent or irregularly clustered (Z). 

 U. Colonies motile, each cell with 2 cilia (V). 



U. Colonies often free but not spontaneously motile, without cilia (c). 



V. Colony (cKnobiuni) spherical or circular (W). 



V. Colony flat, cells 4-16, angles rounded, in a colorless sheath, 



Goniuin, 36 

 W. No gelatinous coating; cells many on a hollow globe Volvox, 32 

 W. With gelatinous coating (X). 

 X. Colony ovate or spherical (Y). 

 X. Colony of 8 cells at equal distances around a circle, 



Stephanosphxra, 37 

 Y. Cells 16-32, globose, at regular intervals on a colorless sphere, 



Eudorina, 33 

 Y. Cells 8-16-32-64, globose, crowded, often angular from pressure, 



Pandorina, 34 

 Z. Cells free-swimming (a). 



Z. Cells attached to aerial or to submerged objects (1^). 

 a. Ovate, granular, in a hyaline, obtuse sheath; contractile vesicle 



present .... Chlamydomonas, 39 



a. Cylindrical, straight or curved, ends sometimes spinous, 



Ophiocytium, 47 



a. Spherical, 3-15/t in diameter . Protococcus, 49 



a. Spherical, 100-150/* in diameter EremosphcBra, 65 



a. Compressed, 3-4-8 angled, angles often produced or bifid, 



Polyedriuni, 50 



b. Aquatic; form variable, cells not spinous, usually stipitate, 



Characium, 48 

 b. Aquatic; form variable, cells often with a dorsal spine, 



Aphanochcete, 20 

 b. Aerial; cells circular, flat, numerous, becoming red by exposure, 



Protococcus, 49 



