32 



TREE PRUNING. 



trunk should be headed in, as well as branches with 

 too great a tendency to droop unnaturally ; generally, 



Fig. 26. Effect of preserving a vertical secondary branch on the 

 upper side of a shortened main branch. A. Branch thus retained, ex- 

 cessively developed at the expense of the rest of the tree. B. Sap lifter of 

 the right size left on the lower side of the main branch to insure its 

 development. 



It will only be necessary to shorten such branches 

 to induce them to reassume a natural direction of 

 growth. 



When several branches have been developed from 

 one node, forming what botanists call a whorl, they 

 should not all be cut away at the same time, lest the 

 circulation of sap be checked by the destruction of 

 bark (and consequently of cambium layer) over too 

 large a surface. 



All dead and d}dng wood should be removed by 

 the workmen in descending the tree ; lichens, and 

 other parasites which interfere with the growth of 

 young trees, should be knocked off with the back 

 of the pruning knife ; and the Mistletoe, the most 

 destructive of all parasites to tree life, should be 



