WISCONSIN PHYTOPLANKTON 



Class CHLOROPHYCEAE. 



Cells with the coloring matter restricted to definite bodies that are 

 grass-green in color (chloroplasts). Cells free-floating, sessile, epi- 

 phytic, epizootic, or endophytic ; solitary, in microscopic to macroscopic 

 colonies of definite or indefinite shape that are naked or enclosed by a 

 hyaline to colored, homogeneous or lamellated, firm or gelatinous en- 

 velope. Colonies with all of the cells morphologically alike or differen- 

 tiated. Colonies growing in all directions; forming simple, laminated, 

 or parenchymatous plates; or developing into simple or branched fila- 

 ments. Cells motile throughout the whole life history, for a portion 

 of it, or immobile at all times. Cells variously shaped ; spherical, hemi- 

 spherical, ovoid, ellipsoid, spindle-shaped, acicular, renifonn, angular, 

 irregular, cylindrical, conical, simple to branching tubular, or con- 

 stricted to form two symmetrical halves of various shapes. Cells con- 

 taining one or more disciform, laminate, cup-shaped, astral, ribbon-like, 

 or reticulate chloroplasts that are parietal, axial, or central in position 

 and have one or more centers for the synthesizing of starch (pyrenoids) . 

 Assimilation product oil in a few cases. Cells uninucleate or multinu- 

 cleate (coenocytic) ; containing a central vacuole, numerous small vacu- 

 oles, or without vacuoles. Contractile vacuoles chiefly confined to the 

 motile genera. 



Asexual reproduction by vegetative cell division, aplanospores, zoo- 

 spores, or akinetes. 



Sexual reproduction by isogamous or heterogamous zoogametes, isoga- 

 mous aplanogametes, or heterogamous motile antherozoids and immobile 

 oospheres. Zygotes germinating immediately, or after a period of rest ; 

 with a direct or an indirect germination into the plant body. 



KEY TO THE DIVISIONS 



Sexual or asexual reproductive bodies with 2-4 cilia of equal length. . ISOKONTAE 

 Sexual or asexual reproduction by non-ciliate reproductive bodies AKONTAE 



Division ISOKONTAE. 



Cells solitary or in colonies and showing the same great range of 

 Tariation in shape, organization of the colony, interior structure, and 

 method of reproduction noted in the description of the class. 



Included in this division is the important plankton family of the 

 Autosporaceae where no motile phase of reproduction is known. The 



