140 Senate 



tree, so many organs of waste are cut off ; and it has been particu- 

 larly insisted upon, that by the excision of large branches, the supply 

 of sap and nourishment which went to their support, would cause a 

 proportionate increase of stem. The results of experience, it may be 

 unnecessary to add, prove this opinion to be erroneous in principle, 

 and that when a branch is cut off, a portion of nourishment to the 

 stem is also cut off from the junction downwards to the root. Every 

 branch of a tree, of whatever size it may be, not only draws nourish- 

 ment and increase of substance from the stem and its corresponding 

 root, in proportion to its size, but also supplies them, in return, with 

 a due proportion of nutriment, and by which their substance is 

 increased J for if an overgrown branch of a thrifty tree be pruned off, 

 the annual increment of the diameter of the stem is found not to 

 exceed the previous rate of growth; or, the excess, if any, is not 

 equal to the amount of wood which had been periodically formed by 

 the branch or branches thus separated from the stem. 



The most favorable season for pruning, in general, is when the trees 

 are in leaf, and their vitality is in full action. For in many instan- 

 ces, as in the oak and walnut tribes, if performed during the dormant 

 periods of the year, an incipient decay of the surface of the wound 

 takes place, and the bark below loses its vitality, and the wound soon 

 becomes enlarged to a considerable extent downwards; and in addi- 

 tion to the space occupied by the branch, it exposes a portion of the 

 surface of the stem to the action of air and moisture, which in time 

 decays and leads to final destruction. On the contrary, this rarely 

 occurs in a vigorous tree that has been pruned in summer, soon after 

 the expansion of the leaves, when the vital functions are in full acti- 

 vity, and the layer of alburnum or young wood has already begun 

 to be formed, and which may be seen around the edges of the wound. 

 As the season advances, the wound becomes more and more covered 

 by the young wood, which, by the end of the summer, will be so far 

 ripened as to protect the bark from the effects of moisture and winter 

 frosts. The proper time for performing this operation is when the 

 leaves have acquired one-half or three-fourths of their natural sizes- 

 There is another advantage also attending this period of pruning, in 

 enabling the operator to free the trees from an excess of jfoilage, and 

 to give proper weight and symmetry to their heads. These principles 

 have been deduced from experience, and are strictly in accordance 

 with the laws of vegetable physiology. If the branch, whether large 

 or small, acted merely as a drain on the vessels of the stem and root, 

 and if the sap it derived from them were elevated to the leaves of 

 the branch, and from thence returned no farther than the origin or 

 point of union with the stem, then the common opinion would be 

 correct. 



On the contrary, however, when it is found that the existence 

 and increase of every branch, twig, and leaf, depends on a com- 

 munication with the root, and that this communication passes 

 through the stem downwards to that organ, and from it upwards 

 periodically; and, moreover, that every periodical series of vessels 



