272 AGRICULTURE. 



Pruning is an important factor in regulating 

 and, in a measure, controlling these two adverse 

 tendencies of the plant to suit man's purposes. 



3. Another point which must not be over- 

 looked is the ^mutual relation between root and 

 top. In the normally developed plant there is a 

 state of equilibrium between the leaf-system and 

 the root-system. As the top develops there 

 must be a corresponding development of roots 

 to supply the crude material to be converted 

 into food by the leaves, and in turn there must 

 be a corresponding growth of the leaf-system 

 if the root-system is to be enlarged in order to 

 convert the crude material into food for the 

 growth of new roots. Hence, when this equi- 

 librium is disturbed, either accidentally or on 

 purpose, the plant bends its energies to restore 

 it. Thus it is that pruning the roots checks 

 the growth of top, and pruning the top not only 

 checks the growth of roots, but gives increased 

 food supply to the remaining parts. 



A. HOW TO PRUNE. 



I. Nature of the Wound. 



It will be seen from a careful study of a cross- 

 section of astern (Fig. 89), that in order for the 

 cut surface to heal it must be in direct commu- 

 nication with the cambium layer of the support- 

 ing stem. 



i. Function of the Cambium. The process 



