152 FORESTRY INVESTIGATIONS U. S. DEPARTMENT OP AGRICULTURE. 



assured in the larger tree. Generally speaking, the best time for plentiful production is neither 

 near the beginning nor near the end of the life of the tree, but when it is in its most vigorous 

 growth, and probably after it has attained its maximum annual height growth, for then its activity 

 is concentrated upon the development of its interior and diameter development. 



If the analyses referred to before exhibit the true amounts of resin formed in the part of the 

 tree from which they are taken, and if our proposition be true that ordinarily resins do not wander 

 in the tree but remain where they are formed, then we could, by analyses of cross sections, dividing 

 them into periods and ascertaining the resm contents of each division, appioximately determine 

 the period of greatest production. In view of the great variation in resin contents, a very large 

 number of analyses would be required to allow generalization. From those at hand it would 

 appear that the time of greatest production falls for the longieaf pine between the seventieth and 

 ninetieth yeais. Since, however, resin production appears to be a result of vigorous life functions, 

 and since wood production depends upon the same conditions, we should rather seek a criterion 

 for resin production in the relation of diameter to age *\; that is to say, whenever the largest 

 amount of wood is formed in a given time — whenever * reaches its greatest value — then the largest 

 amount of resin is presumably also formed. Investigations in this direction are still wanting. 



Another consideration is that of the value of the tree after it has been bled. Since the wood 

 which is formed after the bleeding either on or between the scars is of little value for sawmilling, 

 no trees should be bled — unless they are otherwise unfit for lumber — that will not make good 

 saw logs from the heartwood; that is to say, they should be at least 14 inches in diameter, so as 

 to furnish a log of at least 8 inches at the small end. If the diameter were allowed to increase to 

 at least 18 or 20 inches, probably the largest value both in resin and lumber might be attained. 



In practice, various rules have found acceptance. In France 14 inches, which may be attained 

 in thirty years, is considered a necessary diameter in order to endure continued tapping without 

 injury to life; the lumber value of the maritime pine, being small, enters hardly into consideration. 

 In Austria the tapping is begun with trees as low as 8 inches in diameter, but a diameter of at 

 least 10 inches is preferred. With the spruce, 12 inches is considered a minimum size. In the 

 United States, where no regard to consequences for the tree or lumber is had, the diameter at 

 which a tree might be tapped is gauged by the amount of resin obtained in proportion to the labor 

 expended. "Until lately small diameters were avoided, but now any tree capable of carrying a 

 bore is tapped and the ruin of the future of the industry prepared by this malpractice. 



Size and number of scars and progress of chips. — Regard to the life of the tree and the length 

 of time for which it is expected to produce, on one hand, and the rapidity with which the largest 

 amount of resin can be extracted in the shortest time, on the other hand, determine the size 

 and number of scars inflicted simultaneously. Although the resin itself is or seems to be of no 

 particular use to the tree in its vital functions, by laying bare a part of the cambium and young 

 wood a diminution of the flow of water to the crown, and of nutritive material downward, must 

 be induced. As a result the foliage must suffer in proportion, and with it not only the life of the 

 tree, but also the production of additional resin, which is pioduced in quantity only in vigorously 

 growing trees with a luxuriant foliage. Hence both the life of the tree and the total yield of resin 

 may be curtailed by too many and too large scarifications. 



Since there is a relation between the amount of active foliage on each side of the tree and the 

 activity in the cambium on the same side (one sided crowns produce one-sided annulation), it 

 stands to reason that a larger product can be obtained for a longer time by inflicting a number of 

 smaller scars than by making a large scar on one side of the tree, which is bound to reduce the 

 activity of the foliage on that side, and thereby the production of additional resin; not that the 

 dripping itself increases the production of new resin, as has been sometimes thought, but new resin 

 is formed every year in proportion to the activity of the foliage, and hence by impairing this activity 

 the amount of new resin in the new wood is reduced. 



As we have shown, the resin which the orehardist takes from the tree, in the longieaf pine, 

 at least, comes alone from the sapwood, the heartwood being impregnated with nonfluid oleoresin 

 and not contributing toward the flow. The resin tapped is not only that which was deposited in 

 the sapwood m former years, but also that which is formed during the years of tapping by the 

 growth of the tree; hence sufficient amount of active cambium and young wood should be left 

 untouched to permit a plentiful supply of water from the ground and vigorous function of the 



