26 ALGAE IN PHYTOPLANKTON OF THE UNITED STATES 



Division Chlorophyta 

 Class Chlorophyceae 

 Order Chlorococcales 

 Family Scenedesmaceae 

 GENUS CRUCIGENIA Morren, 1830 (fig. 7) 



MORPHOLOGY 



Cells, 4-10 ^m in diameter, are elliptical, triangular, trapezoidal, or 

 semicircular in surface view. One to 4 cup-shaped chromatophores are 

 situated parietally in each cell. Cells are joined quadrately to form a 

 4-celled coenobia. Several coenobia may be enclosed in a gelatinous 

 envelope. 



REPRODUCTION 



The protoplast divides into 4 autospores that remain quadrately ap- 

 posed. 



OCCURRENCE 



Free-floating colonies occur commonly in the euplankton. It is widely 

 distributed. 



ENVIRONMENTAL CONDITIONS 



Standard 

 Range Mean deviation 



Temperature degrees Celsius 0.0 



pH 4.7 



Dissolved oxygen milligrams per liter .5 



Specific conductance micromho 10 



Total alkalinity milligrams per liter 



Total hardness do 5 



Total nitrogen do .03- 



Total phosphorus do .0 



SPECIES INFORMATION 



Refer to Smith (1920, 1926) and Prescott (1962). 



