66 ALGAE IN PHYTOPLANKTON OF THE UNITED STATES 



Division Chrysophyta 

 Class Bacillariophyceae 

 Order Centrales 

 Family Coscinodiscaceae 

 GENUS CYCLOTELLA Kiitzing, 1834 (fig. 27) 



MORPHOLOGY 



Discoid, drum-shaped cells are solitary (generally), filamentous, or in 

 a colonial gelatinous envelope. The valve view is circular or rarely ellip- 

 tical. Ornamentation is in 2 concentric regions: the outer region is 

 radially striate or punctate, and the inner region is smooth or very fine- 

 ly punctate. Intercalary bands are lacking. There are numerous small, 

 discoid chromatophores. 



REPRODUCTION 



A single auxospore is formed within a cell. 



OCCURRENCE 



The genus is widely distributed in all types of surface waters. 



ENVIRONMENTAL CONDITIONS 



Standard 

 Range Mean deviation 



Temperature degrees Celsius__ 0.0 - 37.0 



pH 3.4 - 10.0 



Dissolved oxygen milligrams per liter .1 - 22.0 



Specific conductance micromho__ 10 -49.800 



Total alkalinity milligrams per liter - 500 



Total hardness do 3 - 2,000 



Total nitrogen do .00- 41.0 



Total phosphorus do .0 - 4.0 



SPECIES INFORMATION 



Refer to Boyer (1927a). 



