74 ALGAE IN PHYTOPLANKTON OF THE UNITED STATES 



Division Chrysophyta 

 Class Bacillariophyceae 

 Order Pennales 

 Family Cymbellaceae 

 GENUS EPITHEMIA de Brebisson, 1838 (fig. 31) 



MORPHOLOGY 



The solitary cells are commonly epiphytic upon submerged 

 macrophytes. They are attached at the girdle, are rectangular in girdle 

 view, and have smooth girdles and intercalary bands. Valves are slight- 

 ly to strongly curved dorsally convex, and ventrally straight to con- 

 cave. Poles are broadly rounded to capitate and sometimes recurved. 

 The axial field is next to the concave side, but its central portion bends 

 sharply inward to form a V-shaped structure midway between the 

 poles. A raphe contains polar and central nodules. Transverse septa ap- 

 pear as costae and alternate with 2 or more rows of punctae. There is 

 generally a single chromatophore next to the concave girdle side, which 

 has irregular projections extending along both valve faces. 



REPRODUCTION 



Protoplasts of approximate frustules each form 2 gametes, which 

 unite to form 2 auxospores. 



OCCURRENCE 



The genus is widely distributed, particularly in the tychoplankton. 



ENVIRONMENTAL CONDITIONS 



Standard 

 Range Mean deviation 



Temperature degrees Celsius 0.0 



pH 3.7 



Dissolved oxygen milligrams per liter 3.9 



Specific conductance micromho 30 



Total alkalinity milligrams per liter 



Total hardness do 5 



Total nitrogen do .00 



Total phospnorus do .0 



SPECIES INFORMATION 



Refer to Meister (1912), Boyer (1927a), and Patrick and Reimer 

 (1966). 



