70 BINDING ACTION OF ROOTS, 



maples, and beeches where enlargements of the roots at the base 

 of the trunk rise up like girders, bracing the tree against winds. 

 More marked illustrations appear ia many tropfcal plants, as the 

 stilt roots of the mangrove and screw pines, and the buttressing 

 roots of one of the Indian rubber plants (Ficus), etc. In the 

 banyan tree of India the branches have an almost unlimited 

 lateral growth owing to the fact that they are supported by a 

 succession of roots that reach from the branches to the ground. 

 Kerner cites an example of one of these trees with 300 large and 

 3,000 small prop roots. This tree sheltered a village of 100 native 

 huts and an army of 5,000 men. 



30. Binding Action of Roots. — The landscape would be con- 

 stantly subject to great change either by erosion or through the 

 action of winds were it not for the solidifying and binding action 

 of roots upon the soil. The difficulty of breaking up the prairies 

 and the turf of abandoned fields or meadows indicates the extent 

 and completeness of the ramifications and interweaving of the 

 roots. Miles of sandy reaches are held from shifting through 

 the restraining action of roots and stems of grasses and other 

 plants. The little town at the end of Cape Cod would have been 

 submerged long ago by the shifting sand dunes had not suitable 

 plants been planted to hold in check the loose sands. 



Roots not only bind the soil together but the older portion of 

 the root usually possesses the power of contraction. This pro- 

 perty results in the pulling down and fixing of the stem in the 

 ground. You must have often wondered how stems and bulbs 

 become so deeply buried in the soil although the seeds are 

 scattered on the surface of the soil. This is also well illustrated 

 in the tips of raspberry bushes which come in contact with the 

 soil through the bending of the stalk. Roots strike out from the 

 tip and when thoroughly established in the earth the older 

 portions contract and bury the tip in the soil. In the same 

 way seedlings of various plants are slowly pulled down into the 

 earth so that they finally become planted at considerable depths. 

 It is this contraction of the roots that keeps the slowly elongating 

 stems of the dandelion, dock and many other plants buried in 

 the soil and that binds many creeping plants such as certain 

 clovers and knot weeds firmly to the earth. 



