46 ALGAE IN PHYTOPLANKTON OF THE UNITED STATES 



Division Chlorophyta 

 Class Chlorophyceae 

 Order Chlorococcales 

 Family Oocystaceae 

 GENUS SELENASTRUM Reinsch, 1867 (fig. 17) 



MORPHOLOGY 



Cells are arcuate to lunate with apices acutely pointed. The single 

 chromatophore is parietal. Convex surfaces of 4, 8, or 16 cells are ap- 

 posed; a colony may have as many as 100 or more cells. There is no 

 gelatinous envelope. 



REPRODUCTION 



The cell contents divide into 4, 8, or 16 autospores, which generally 

 remain opposed to one another following release from the parent-cell 

 wall. 



OCCURRENCE 



Selenastrum is widely distributed in the euplankton. It is found spar- 

 ingly intermingled with other free-floating algae in pools and other 

 quiet waters (Smith, 1950). Some species occur in soft, acidic waters. 



ENVIRONMENTAL CONDITIONS 



Standard 

 Range Mean deviation 



Temperature degrees Celsius 0.0 - 



pH 4.4 - 



Dissolved oxygen milligrams per liter .4 ■ 



Specific conductance micromho 25 



Total alkalinity milligrams per liter 



Total hardness do 4 



Total nitrogen do .00- 



Total phosphorus do .0 - 



SPECIES INFORMATION 



Refer to Collins (1909), Smith (1920), and Prescott (1962). 



