64 (iEIfEBAL PEINCIPLKS. 



internal structure is, essentially, like that of the stem, 

 which Avill be described further along. The material for 

 the growth of the root is supplied by the stem and leaves 

 above, and these, in turn, are furnished, with the crude 

 material for their own support and enlargement by the 

 roots. The parts of the tree above the surface of the 

 ground, and those below it, are dependent each upon the 

 other for growth and existence. Practical cultivators 

 are familiar with many facts that illustrate the intimate 

 relations and mutual dependency of the roots and stems. 

 For instance, where one portion of the head or branches 

 is much larger or more vigorous than the other, if the 

 roots be examined, it will be found that those immedi- 

 ately under, or in direct connection with the largest 

 branches, will have a corresponding size and vigor. In 

 cases where one side of the top of a large tree is cut oiF, 

 as in top grafting, a large number of new shoots are pro- 

 duced on the cut branch, and, if the roots be examined 

 under, or in connection with this branch, a corresponding 

 new growth will be found there. It is quite obvious, 

 from these and similar facts, that whatever affects the 

 roots or stems of trees, favorably or unfavorably, affects 

 the whole tree. If the foliage of a tree be entirely re- 

 moved in the growing season, the absorbent action of the 

 roots is suspended ; and if the absorbing portions of the 

 roots be cut off, the growth of the top instantly ceases. 



Section 2. — The Stem. , 



The Stem is that part of a tree which starts from the 

 collar, and grows upwards. It sustains all the branches, 

 and forms the medium of communication between the 

 different parts of the tree, from one extremity to the 

 other. 



Plants, like the grape, with twining, or climbing stems, 

 are called vines; and such as have no main stem, but have 



