THE REPAIR AND REPLACING OF TREES 



225 



being overthrown by strong winds as trees of which the 

 trunks are hollow shells. The concrete acts as a pillar 

 which reenforces the tree. 



Knot-Holes. — Equally as serious and more numerous than 



Fig. 34. — 1. Methods of strengthening a weak crotch : A, by means 

 of a boh. B, by means of hook-bohs and chain. 2. Vertical 

 section of branch, showing method of bolting. A, Wood. B, 

 Bark. C, Bolt. D, Cement. E, Washer and nut. Healing 

 tissue will overcap the cement. 



wounds on trunks of trees are knot-holes caused by the 

 decay of stumps left by improper pruning. In these cases 

 the grain of the wood running toward the centre of the tree 

 instead of vertically, the decay is more easily carried to the 



