12 BUIXETIX 1064, U. S. DEPARTMENT OF AGEI CULTURE. 
occurred. Here, as in the case of the pines, and even in that of the 
conifers studied by Tsehirch 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 (PI. II. fig. 3) and are often arranged in rather continu- 
ous tangential series (PI. 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. 
STAXDABD PEACTICE. 
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 Xo. 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 
a For. Serv. Bui. 90, p. 27. 
