WISCONSIN PHYTOPLANKTON 27 



Family CHROOCOCCACEAE. 



Cells not differentiated into an apical and basal portion ; rarely soli- 

 tary, generally in colonies of definite or indefinite shape and always 

 enclosed by a gelatinous sheath. Cell shape various, and cellular ar- 

 rangement within the colonial envelope definite or indefinite. 



Asexual reproduction by vegetative cell division and the fragmenta- 

 tion of the colonies. Gonidia formation occasionally taking place in 

 certain genera. 



KEY TO THE GENERA. 



Cells solitary or in colonies that never contain more than a few cells. 



Cells spherical or hemispherical CHEOOCOCCUS 



Cells longer than they are broad. 



Individual cells or groups of cells enclosed by a gelatinous 



vesicle GLOEOTHECB 



Individual cells or groups of cells without vesicles. 



Ends of cells rounded RHABDODERMA 



Ends of cells pointed DACTYLOCOCCOPSIS 



Cells always in colonies that contain many cells when mature. 

 Cellular arrangement within colony definite. 



Cells forming a flat plate MERISMOPEDIA 



Cells forming a hollow sphere one cell in thickness. 



Center of colony with radiating gelatinous strands . GOMPHOSPHAERIA 



Center of colony without radiating strands CoELOSPHAERnrM 



Cellular arrangement within colony indefinite. 

 Cells spherical. 



Cells densely aggregated MICBOCYSTIS 



Cells some distance from one another APHANOCAPSA 



Cells longer than they are broad APHANOTHECE 



CHROOCOCCUS Nageli 1849. 



Cells spherical, usually hemispherical for some time after division; 

 solitary or 2-48-16 or more united in colonies enclosed by a hyaline 

 or colored, homogeneous or lamellated sheath; free-floating, sessile, or 

 epiphytic. Individual cells of colony at times surrounded by a homo- 

 geneous or lamellated sheath. Cell contents grey, grey-green, blue- 

 green, olive-green, yellowish, orange, reddish or violet in color; homo- 

 geneous or granular. 



Reproduction by vegetative division of cells in three directions. 



KEY TO THE SPECIES. 



Sheaths enclosing cells homogeneous. 



Cells solitary, in twos, and in fours C. MINUTUS 



Cells in colonies of 4-8-16 or more. 



Individual cells or groups of cells some distance from one 



another C. DISPEBSUS 



Individual cells or groups of cells fairly close together. .C. LIMNEHCUS 



