56 Plant Life and Evolution 



ity of the plant body is usually associated with the 

 increase in the amount of green tissue. The most 

 important function of the plant's life, aside from 



FIG. 4 



Evolution of the plant body in the lower green plants. 



A Unicellular plant (Pleurococcus). 



B Unbranched filament, with basal root-like organ, or hold 

 fast (r) (CEdogonium). 



C A confervoid alga, Draparnaldia, in which there is a 

 photosynthetic apparatus consisting of tufts of densely 

 crowded green cells, Cl. 



reproduction, is the process of photosynthesis ; hence 

 the adjustment of the green cells to the light ex- 

 posure is of prime importance, and this adjustment 

 explains some of the most striking modifications of 



