68 ALGAE IN PHYTOPLANKTON OF THE UNITED STATES 



Division Chrysophyta 

 Class Bacillariophyceae 

 Order Pennales 

 Family Cymbellaceae 

 GENUS CYMBELLA Agardh, 1830 (fig. 28) 



MORPHOLOGY 



Solitary cells are free floating, attached at the ends of gelatinous 

 stalks, or contained within branched gelatinous tubes. Cell is 

 longitudinally asymmetrical in valve view and is lunate, subellipitical, 

 rhombic, or naviculoid. It is ventrally concave and dorsally convex. The 

 raphe is curved and contains well-defined nodules. Ornamentations 

 consist of radiating transverse striae or punctae. Intercalary bands are 

 lacking. A single chromatophore is plate shaped. 



REPRODUCTION 



Two gamates are formed from the protoplast of 2 approximate cells 

 and unite to form 2 auxospores. 



OCCURRENCE 



A distinctly freshwater genus, Cymbella is widely distributed in the 

 euplankton. 



ENVIRONMENTAL CONDITIONS 



Standard 

 Range Mean deviation 



Temperature degrees Celsius 0.0 - 



pH 3.4 - 



Dissolved oxygen milligrams per liter 1.1 - 



Specific conductance micromho 10 



Total alkalinity milligrams per liter 



Total hardness do 3 



Total nitrogen do .00- 



Total phospnorus do .0 - 



SPECIES INFORMATION 



Refer to Boyer (1927a). 



