278 PRUNING. 



sects, which hasten the destruction of the tree. The 

 dead bark should be entirely removed, even should it 

 be necessary in doing so to make large wounds. At- 

 tention, too, should be given to injuries to the bark 

 caused by the fall of neighbouring trees. These may 

 remain hidden for years, and are often only detected 

 by the peculiar sound produced by a blow of the 

 pruning-knife. 



" Cavities in the Trunk. — Very often, when a tree 

 has been long neglected, the trunk is seriously injured 

 by cavities, caused by the decay of dead or broken 

 branches. It is not claimed that pruning can remove 

 defects of this nature : it can with proper applications, 

 however, arrest the progress of the evil, and in such 

 cases should always be resorted to. The edge of the 

 cavity should be cut smooth and even, and all decom- 

 posed matter, or growth of new bark formed in the 

 interior, should be carefuUy removed. A coating of 

 coal-tar should be applied to the surface of the cavity, 

 and the mouth plugged with a piece of well-seasoned 

 oak, securely driven into place ; the end of the plug 

 should then be carefully pared smooth and covered 

 with coal-tar, precisely as if the stump of a branch 

 were under treatment. If the cavity is too large to 

 be closed in this manner, a piece of thoroughly sea- 

 soned oak-board, carefully fitted to it, may be securely 

 nailed into the opening, and then covered with coal- 

 tar. It is often advisable to guard against the 

 attacks of insects, by nailing a piece of zinc or 

 other metal over the board, in such a way that the 

 growth of the new wood will in time completely 

 cover it. 



" These operations resemble, if such a comparison 



