244 PRUNING. 



Another case for pruning is that of branches having 

 become dead upon a tree. So long as the branches are 

 vital, they are in a state of growth and enlargement, 

 forming woody layers along with, and in conjunction 

 with, the trunk of the tree, whence they issue ; but as 

 soon as life ceases in the branch, the annual layers of 

 wood upon the trunk, by continuing to increase gradu- 

 ally, absorb the base of the dead branch attached to 

 it, and which, when enveloped in the wood of the 

 trunk, forms the said lamented black knot. If this 

 occurs in a young tree, while the branch is a compara- 

 tive sapling without heart-wood, it soon decays and 

 falls off without any serious consequence ; but when a 

 large branch dies upon a tree after the heart-wood is 

 formed in it, an evil of no small magnitude is incurred. 

 The dead branch in this state remains upon the tree 

 for many years, till embedded deeply in the trunk. 

 The consequence is, that when the tree is sawn into 

 boards or thin scantlings, a black knot is frequently 

 found to go right through it, and on the wood being 

 seasoned it frequently falls out, thereby leaving a 

 hole in the wood, and rendering it useless for many 

 purposes. Therefore, in all cases of young growing 

 plantations, we at once prune off all decayed branches 

 from the main body of the tree; it is not necessary 

 to prune branches off branches, or even off small limbs, 

 but only off those parts of a tree which yield timber 

 proper. In priming off dead wood from young trees, 

 we use only the pruning-knife or chisel ; but when 

 the trees are aged, and the heart-wood formed in the 

 branches, the operation is performed by other means. 



It is often difficult to say what the truly natural 

 habits of trees are, as soil, climate, and situation have 

 each a powerful influence in altering their appearances, 



