THE PLANT BODY 



67 



Second winter 

 (Death) 



f 



Second Summer 

 (Photosynthesis 

 and reproduction) 



FIG. 28. The seasonal history of a biennial plant, White Sweet Clover (Melilotus). 

 (From Densmore.) 



its branches. Roots which rise from such unusual places are 

 called ADVENTITIOUS roots. In certain species the aerial 

 roots hang free in the air and absorb moisture from the at- 

 mosphere. In addition, such roots 

 may develop chlorophyll and so 

 perform the characteristic func- 

 tion of leaves. In the Fig tree the 

 aerial roots grow from the branches 

 down to the earth where they 

 become attached and eventually 

 form a stout trunk which functions 

 as a stem. Comparable to these 

 roots are the so-called BUTTRESS 

 roots of some Palms and of the 

 familiar Indian Corn. (Fig. 29.) 



Many plants depend chiefly or FlG 29 ._ English Ivy , showing 

 entirely on other plants for their the aerial roots which enable it to 



cling to walls. (From Ganong, 

 food materials. The rOOtS Of SUch a f te r LeMaout and Decaisne.) 



