WOUNDS 253 



growth. This becomes evident in the lower region of the stem, 

 where in fact, if pruning is carried far enough, growth may cease 

 altogether, as I have also proved to be the case with trees that 

 are very much overcrowded. 



One must always bear in mind that as pruning generally 

 interferes with growth there must be important reasons for 

 performing the operation if the loss of growth is to be com- 

 pensated for. Amongst these may be mentioned, on the one 

 hand, the improvement of the form of the stem and the 

 production of a clean bole, and, on the other, the admission of 

 light to underwood. 



If, for the purpose of obtaining smooth stems, pruning is 

 carried further than the mere removal of a few branches, one 

 must remember that in such a case there is not only reduction 

 of growth, but that there are also indirect dangers consequent on 

 such pruning. The first of these dangers is connected with the 

 retardation of the healing of the wounds. It is evident that 

 the formation of callus over a branch-wound depends to a large 

 extent on the supply of plastic substances with which the 

 cambium along the edge of the wound or the callus-cushion is 

 provided. Very severe pruning will seriously interfere with the 

 formation of callus, and consequently with the occlusion of 

 wounds. This leads us to consider whether the pruning of the 

 stem to the desired height should not be accomplished in two 

 operations, separated by an interval of several years. If one first 

 of all removes the branches from the lower half of the portion of 

 the stem that it is desired to clear, the diminution of the products 

 of assimilation does not interfere to such an extent with the 

 formation of callus, and the wounds may be covered over in 

 a few years. The more vigorous development of the crown 

 compensates to a certain extent for the branches removed by 

 pruning, so that when the operation is repeated the new wounds 

 close sooner than would have been the case had the whole 

 operation been performed at one time. 



By dividing the operation in this way there is also much less 

 chance of an excessively large number of epicormic shoots being 

 produced. Such shoots originate partly in the adventitious 

 buds of the callus along the edge of the wound, and partly in 

 dormant eyes. In the latter case, it is chiefly the buds that are 



