100 WISCONSIN PHYTOPLANKTON 



KEY TO THE FAMILIES. 



Asexual reproduction by zoospores. 



Cells epiphytic or endophytic PLANOSPOBACEAE 



Cells or colonies free-floating. 



Colonies capable of growth by cell division PALMF.T.T.ACEAS 



Colonies incapable of growth by cell division HYDBODICTYACEAE 



Asexual reproduction by autospores or division of cells. 

 Cells capable of vegetative division. 



Solitary, in regular masses, or in strata PBOTOCOCCACEAE 



In colonies held together by remains of old cell walls. . DICTYOSPH AKRIACEAE 

 Cells incapable of division except to form autospores AUTOSPORACEAE 



Family PALMELLACEAE. 



Cells spherical, ovoid, or reniform; rarely solitary, generally united 

 to form, colonies which, are at times of macroscopic size. Colonies al- 

 ways embedded in a gelatinous matrix. Colonies capable of an in- 

 crease in size by the vegetative division of the constituent cells. Chloro- 

 plasts generally single, cup-to disc-shaped and parietal ; or star-shaped 

 and central ; with or without pyrenoids. 



Reproduction by the fragmentation of the colony or by zoospores. 



Sexual reproduction known in certain genera. 



KEY TO THE GENERA. 



Chloroplast star-shaped and central ASTEEOCOCCTJS 



Chloroplast cup- to disc-shaped and parietal. 



. Cells with pseudocilia TETBASPOBA 



Cells without pseudocilia. 



Gelatinous envelope of colony lamellated GLOEOCYSTIS 



Gelatinous envelope of colony homogeneous. 

 Cells spherical. 



Chloroplast of old cells cup-shaped SPHAEROCYSTIS 



Chloroplast of old cells disciform PLANKTOSPHAEBIA 



Cells ovoid to reniform GLOEOCYSTOPSIS 



GLOEOCYSTIS Nageli 1849. 



Cells spherical; solitary or in small colonies of eight cells or less. 

 Each cell and the whole colony surrounded by a hyaline, lamellated, 

 gelatinous sheath. Chloroplast of young cells cup-shaped, parietal, and 

 with one pyrenoid ; generally diffuse and rich in starch in old cells. 



Asexual reproduction by a fragmentation of the colony through the 

 softening of the gelatinous envelope, or by zoospores. Akinetes known. 



