3^ 



PLANT BIOLOGY 



Some plants bear aerial roots, that may propagate the 

 plant or may act as braces. They are often called prop-roots. 

 The roots of Indian corn are familiar (Fig. 38). Many 

 ficus trees, as the banyan of India, send out roots from 

 their branches ; when these roots reach the ground they 

 take hold and become great trunks, thus spreading the 

 top of the parent tree over large 

 areas. The muscadine grape of the 

 Southern states often sends down 

 roots from its stems. The man- 

 grove tree of the tropics grows along 

 seashores and sends down roots 

 from the overhanging branches 

 (and from the fruits) into the shal- 

 low water, and thereby gradually 

 marches into the sea. The tangled 

 mass behind catches the drift, and 

 soil is formed. 



Adventitious Roots. — Sometimes 

 roots grow from the stem or other 

 unusual places as the result of some 

 accident to the plant, being located 

 without known method or law. 

 They are called adventitious (chance) 

 roots. Cuttings of the stems of 

 roses, figs, geraniums, and other plants, when planted, 

 send out adventitious roots and form new plants. The 

 ordinary roots, or soil roots, are of course not classed as 

 adventitious roots. The adventitious roots arise on occa- 

 sion, and not as a normal or regular course in the growth 

 of the plant. 



No two roots are alike ; that is, they vary among them- 

 selves as stems and leaves do. Each kind of plant has its 





Fig. 38. — Indian Corn, 

 showing the brace roots 

 at 00. 



