creases in 1917 were less indicative, but increases were more significant, since normal diameter growth was relatively low in that year. It was observed that, regardless of the method used, the response, after turpentining, of trees with very narrow annual rings often was to produce much wider rings than before; whereas the trees with exceedingly wide rings and very heavy summer wood often showed marked reduction in the wood formed after turpentining. A tendency toward more vigorous responses was observed on the south side of trees, as contrasted with the north side. Very great variation in wood formation and productive power was observed in individual trees in the same environment. No satisfactory means was found, however, of positively determining in advance the productive power of a tree. Marked variations in the wood formation on different sides of a tree, at different parts of the streak, and at different heights, were noted. The study of specimens obtained month by month at different heights was therefore more enlightening in many respects than observations made only at the end of the season. MISCELLANEOUS OBSERVATIONS. No consistent relation between width of ring and number of resin passages resulted from an analysis of the data available on this subject. No indication of a structure corresponding in any way to the "resinogene Schicht" of Tschirch was observed. The first formation of wood in the region of the trunk where turpentining is carried on was observed, in 1916 and 1917, to take place not earlier than April 8 to 10; and from that time on in different trees it continued until by the middle of May it had begun in practically all trees. Wood cells or tracheids for the most part formed before resiniferous tissue. The first formation of resiniferous tissue occurred between the middle of April and the end of May. Finally, turpentining gives an additional product and profit from the forest before the trees are cut into lumber. This gain may be obtained, at least in the case of well-managed, large, mature timber, without reducing its strength, or appreciably degrading the lumber. The inch or so of the outer sapwood involved in the process of turpentining is removed in the slabs and edgings when the logs are cut up. Poor turpentining methods which kill or dry-face the timber, may produce some degrade due to pitch-streak formation, decay, or excessive insect attack, but this is for the most part unnecessary. The fact that many lumber companies are turpentining their own timber is also a pertinent argument for the practice. Turpentining a given tract should, however, be planned far enough in advance of the cutting of the trees to insure the obtaining of the full advantage of at least a four to six year operation, instead of the sawmill demand forcing the timber to be cut at the height of its gum-producing power. Many other problems, involving the further development of needed improvements in practice, and also many related to a better understanding of the imperfectly known physiological processes fundamental to oleoresin production, await investigation. ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM 20 CENTS PER COPY |