128 ALGAE IN PHYTOPLANKTON OF THE UNITED STATES 



Division Cyanophyta 

 Class Cyanophyceae 

 Order Hormogonales 

 Family Rivulariaceae 

 GENUS RAPHIDIOPSIS Fritsch and Rich, 1929 (fig. 58) 



MORPHOLOGY 



Cells are cylindrical and about 4.5 yim in diameter. They are 1.5-2 

 times as long as wide. The solitary, free-floating trichomes are relative- 

 ly short. The sheath is absent. Both poles of a trichome may be tapered, 

 or one pole may be tapered and the other, broadly rounded. Numerous 

 pseudovacuoles may be present. Akinetes are barrel shaped and are 

 located in the middle of the trichome. 



REPRODUCTION 



The trichome breaks transversely into equal halves. Akinetes may be 

 found midway in the trichome. 



OCCURRENCE 



The trichomes of the genus are free floating. 



ENVIRONMENTAL CONDITIONS 



Standard 

 Range Mean deviation 



Temperature degrees Celsius 0.0 



pH 4.9 



Dissolved oxygen milligrams per liter .1 



Specific conductance micromho 20 



Total alkalinity milligrams per liter 1 



Total hardness do 4 



Total nitrogen do .06 



Total phospTiorus do .0 



SPECIES INFORMATION 



Refer to Fritsch and Rich (1929) and Daily (1945). 



