PROTOPHYTA 



51 



tion of a jelly recalling the palmella phase. Such groups, known 

 as spheroidal colonies, may be provided with flagella, and their 

 movement is active, e.g., Gonium pectorale (Fig. 21) and Uro- 



Fig. 21— GONIUM PECTORALE 



This sixteen-celled colony of one of the green 



plant flagellates is not often caught with all 



of its flagella showing 



From a photomicrograph by the author 

 Magnification, 290 



glenopsis Americana (Fig. 22), or they may be quiescent {e.g., 

 Coelospherium, Microcystis, and Aphanocapsa) . In other cases, 

 as in some types of bacteria, colony formation is due to the 

 adhesion of cells after division, forming so-called "catenoid 



Fig. 22— A YELLOW-COLORED 



PLANT FLAGELLATE, URO- 



GLENOPSIS AMERICANA 



A delicate, gelatinous colony of minute 

 yellow zoospores which are embedded in 

 a gelatinous matrix. Each zoospore con- 

 tains one or more oil globules which are 

 liberated when a colony is broken up in 

 water pipes and cause a fishy odor in 

 the water 



From a drawing by the author 

 Magnification, 250 







o o 



© © 



» Osa^^T 



(chain-like) colonies," in which the cells adhere side by side or 

 end to end (Fig. 24), or "arboroid (tree-like) colonies" in which 

 the cells are attached alternately by stalks or tests* (Fig. 23). 

 Division in two planes gives rise to thallus or plate-like colonies 

 (Fig. 24). Attachment of individuals in a linear series gives 

 rise to filamentous forms, a characteristic of the brown, red, and 

 blue-green algae. 



* Test, the external, firm covering of a cell ; it is not a living part of the cell, and 

 varies in consistency in different forms from rigid to soft and gelatinous. 



