128 



ROOTS 



Stems which are in contact with water are apt to develop 

 what are called water roots. These differ from soil roots 

 in that they occur in dense clusters. Such roots may 

 also develop from the primary roots, as when a root finds 

 its way into a tile drain. A mass of roots may result. 

 Drains are frequently choked up by these water roots. 



Secondary roots may act as tendrils. Tendrils are 

 curving, slender organs which hold climbing plants to the 

 things on which they climb. Probably you have noticed 

 the tendrils of vines. Tendrils are conspicuous on the 

 grapevine and on the climbing cucumber. 

 The poison ivy, the English ivy, and the 

 trumpet creeper are vines whose tendrils are 

 secondary roots. The tendrils of other plants 

 may be modified leaves or may be modified 

 stems. 



C. Branches of Roots. — The branches of 

 roots do not arise from the epidermis of the 

 parent shoot. They arise from the outer- 

 most layer of cells of the stele. (See Fig- 

 ure 41.) Thus they are compelled to begin 

 their burrowing habit even before they enter 

 the soil. The first burrowing they do is 

 through the cortex to the epidermis. With 

 a knife you can easily strip the soft cortex 

 of a young root away from the hard stele. You will then 

 see holes in the cortex which were made by the branches. 

 In this matter of the origin of branches, roots are dif- 

 ferent from stems. As you already know, the branches of 

 stems first appear as buds in the axils of the leaves. They 

 arise near the surface. 



Fig. 41. — Dia- 

 gram showing 

 the origin of 

 the branches 

 of roots. 



