THE FRESH-WATER ALGAE 



155 



149 (148, 150) Bristles varying in number, without a basal swelling. Cells 

 single Chodatella Lemmermann. 



Cells solitary, ellipsoidal; spines evenly distributed over the 

 surface or in circles about the ends. Chromatophore parietal, 

 with or without pyrenoids. 



Chodatdla is occasionally found in the plankton of larger lakes. 



Fig. 184. Chodatella citriformis Snow. X Soo. (Original.) 



150 (148, 149) Bristles numerous, on the outside of the colony only. Cells 

 usually united into a small cluster by a gelatinous substance. 



Franceia Lemmermann. 



Chromatophores two, each with a pyrenoid. 



This genus in its general characteristics resembles Richteriella 

 but it is distinguished from it by the larger size and oval shape 

 of the cells, the shorter spines and the two chromatophores. 



Reproduction takes place by division in a single longitudinal 

 direction. 



Fig. 185. Franceia sp. X about 600. (Original.) 



151 (138, 142) Cells of some other shape than spherical or elliptical; with 



points or ^.ngles 152 



152 (153, 154) Cells needle-like or fusiform, often variously curved, the length 



often many times the diameter. . . Ankistrodesmus Corda. 



Ankislrodesmus is found in all ponds, 

 lakes, and rivers. It is one of the most 

 common and one of the hardiest of the 

 unicellular algae. 



Fig. 186. Ankistrodesmus. Various species. 

 X 600. OriginaU 



153 (152, 154) Cells short, fusiform, length two to four times the diameter. 



Dactylococcus Nageli. 



Cells free, short, nine to eighteen /x long. Chromatophore with a pyrenoid, 

 opposite to which there is an opening. In reproduction two to eight cells are 

 formed by transverse internal division. 



Fig. 187. Dactylococcus in/usionum Nageli. X 600. (Original.) 



154 (152, 153) Cells distinctly three, to many-angled, angles all in one plane or 



not; at the ends often one or more simple or divided spines. 



Tetraedron Kiitzing. 



Chromatophore single, parietal, usually with a pyrenoid. 



In this genus there is the greatest variety in regard to the shape 

 of the cells, number of points, and size; the most common one is, 

 however, a minute form with but few points. 



Fio. 188. Tetraedron enormfit Bary. X 600. (Original.) 



