64 ALGAE IN PHYTOPLANKTON OF THE UNITED STATES 



Division Chrysophyta 

 Class Bacillariophyce?e 

 Order Pennales 

 Family Achnanthaceae 

 GENUS COCCONEIS Ehrenberg, 1838 (fig. 26) 



MORPHOLOGY 



Solitary cells are transversely rurved in girdle visw and broadly ellip- 

 tical in valve view. Epitheca has an axial pseudoraphe and transverse 

 striae or punctae. Hypotheca has a median raphe that is straight or 

 sigmoid and has a central or polar nodule. Striae and punctae generally 

 are transverse. A single, laminate chromatophore adjoins the epitheca. 



A single auxospore is formed by the conjugation of 2 approximate 



alio 



OCCURRENCE 



Species of the genus are almost exclusively epiphytic upon filamen- 

 tous chlorophytes. It is widely distributed. Occurrence of the genus in 

 the plankton generally results from sloughing of the periphyton. 



ENVIRONMENTAL CONDITIONS 



Standard 

 Range Mean deviation 



Temperature degrees Celsius 0.0 - 34.0 



pH 4.1 - 10.0 



Dissolved oxygen milligrams per liter .8 - 20.0 



Specific conductance micromho 10 -48,000 



Total alkalinity milligrams per liter - 480 



Total hardness do 4 - 2,000 



Total nitrogen do .00- 38.0 



Total phosphorus do .0 - 3.9 



SPECIES INFORMATION 



Refer to Boyer (1927a) and Patrick and Reimer (1966). 



