42 ON THE COMPARATIVE ADVANTAGES OF THE 



not be left to increase their own growth to an extent that will be prejudi- 

 cial to the tree. In order that any system of pruning may contribute 

 in the highest possible degree to the attainment of the fundamental 

 object, it is absolutely necessary that it be in harmony with the laws 

 of vegetable physiology ; and it is only by having an intimate 

 knowledge of the structure and functions of the different organs of 

 trees, that any method of pruning can be founded on sound and 

 definite first principles. 



In trees, as in all other plants, the nutritive organs are the roots, 

 the stem (with the branches), and the leaves. The sap, which is 

 imbibed by the spongioles at the extremities of the roots, ascends 

 the trunk, and enters the branches, at last reaching the leaves, 

 where it combines with the sap which is absorbed from the atmo- 

 sphere through the pores of the leaves : and here the leaves trans- 

 pire all the fluids that are not essential to vegetation, and it is 

 through their instrumentality that the sap is elaborated and changed 

 into the nutritive food of the plant. 



Having given the above statement in regard to the ascension of 

 the sap and the uses of the leaf, we now proceed to compare the 

 system of severe close pruning (i.e., clearing off a great number of 

 the branches from the stem without doing anything to check the 

 growth of contending tops) with the system of foreshortening. 

 The leaves being part of the vital energies of the tree, it follows 

 that to cut off the greater part of the branches and the leaves is just 

 removing a number of the most essential organs, and thereby dimi- 

 nishing the rate of growth to a considerable extent. Close pruning 

 utterly fails in bringing about the object in view, namely, the 

 production of the greatest quantity of sound and clean timber, — 



In/, Because it tends to reduce the vital energies of the tree. 



2c?, It does not check the growth of contending leaders or over- 

 strong side branches, nor prevent them from appropriating the 

 nutriment to increase their own growth rather than that of the stem. 



3'/, It tends to deteriorate the quality of the timber ; for when 

 the wounds made on the stem are greater than can be healed over 

 during the first or second season's growth, the exposed surface 

 gradually becomes less succulent, and ultimately loses its vitality 

 before it can be healed over. "When this is the case, the wounds 

 may be healed over, but no union can take place between the decay- 

 ing surface and the enclosing sapwood ; and this must unquestion- 

 ably cause a blemish, if not a serious defect, in the quality of the 

 timber. And, again, the healing of these wounds is an additional 



