i2 BULLETIN 1064, TJ. S. DEPARTMENT OF AGRICULTURE. 



occurred. Here, as in the case of the pines, and even in that of the 

 conifers studied by Tschirch in midsummer condition, considerable 

 time was required to obtain the major response induced by the wound. 



PART PLAYED BY RESIN PASSAGES FORMED AFTER WOUNDING. 



When the new wood formation begins after wounding, one of the 

 most striking features of the developing ring is the early differentia- 

 tion of more resin passages than are normally found. As soon as 

 these resin passages, induced by wounding, are formed, they add 

 materially to the flow of oleoresin, since they are generally very 

 numerous (PL II, fig. 3) and are often arranged in rather continu- 

 ous tangential series (PL II, figs. 3 and 5). Although a consider- 

 able amount of gum comes from this newly formed resiniferous 

 tissue, it seems doubtful if, as has been stated, it constitutes "the 

 chief source of commercial crude turpentine." 22 The term "sec- 

 ondary resin passages" has been used to describe the resiniferous 

 tissue formed in the annual rings after turpentining. In contrast 

 to this the term " primary resin passages " has been applied to the 

 resin passages present in the round timber. Both these terms seem 

 undesirable, inasmuch as the distinction between the resin passages 

 of the two regions is not clearly defined, and since a certain number 

 of the so-called primary passages would have been present under any 

 circumstances in the new wood. Which these are, it would be im- 

 possible to determine. The types of resin passages found will be dis- 

 cussed with reference to length and number in the following pages. 



RESULTS OBTAINED BY DIFFERENT METHODS. 



EXPERIMENTS AT COLUMBIA. MISS. 



STANDARD PRACTICE. 



The operating methods termed "standard" in this report are the 

 regular methods practiced by the company with which the coopera- 

 tive experiment here described was carried on. The chipping was 

 somewhat heavier than that known as the standard Forest Service 

 method. In the Standard chipping as practiced at Columbia, Miss., 

 the streaks were cut with a No. 2 hack or chipping tool. (See PI. 

 IV, fig. 2.) The weekly streak varied in depth from one-half to 

 three-fourths inch and was about one-half inch in height. The 

 type of forest, as indicated in Plate I, figure 2, consisted of large 

 mature timber, but included also many old but relatively small 

 suppressed trees. The chipping began early in the spring of 1916. 

 The first material for microscopic study was collected in April, 

 after four or five streaks had already been cut. The yield from 



22 For. Serv. Bui. 90, p. 27. 



