70 ALGAE IN PHYTOPLANKTON OF THE UNITED STATES 



Division Chrysophyta 

 Class Bacillariophyceae 

 Order Pennales 

 Family Diatomaceae 

 GENUS DIATOMA DeCandolle, 1805 (fig. 29) 



MORPHOLOGY 



Cells are rectangularly tabular in girdle view and united at the corner 

 into free-floating or sessile zigzag to linear chains. There are 1 to 2 in- 

 tercalary bands. Several transverse septa appear as transverse costae. 

 Cells are lanceolate to linear and bilaterally symmetrical. Valves con- 

 tain transverse, finely punctate striations between the costae. The nar- 

 row pseudoraphe does not have a median expansion. Numerous 

 chromatophores are elliptical. 



REPRODUCTION 



A single auxospore is formed within a cell. 



OCCURRENCE 



The genus is widely distributed in cool water. Some species are in- 

 dicative of particular environmental conditions. 



ENVIRONMENTAL CONDITIONS 



Standard 

 Range Mean deviation 



Temperature degrees Celsius. _ 0.0 - 34.0 



pH 4.4 - Hi.lt 



Dissolved oxygen milligrams per liter 1.2 - 20.6 



Specific conductance micromho__ 12 -43,400 



Total alkalinity milligrams per liter - 420 



Total hardness do 3 - 1,600 



Total nitrogen __do .00- 41.0 



Total phosphorus do .0 - 3.9 



SPECIES INFORMATION 



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



