42 BULLETIN 1064, IT. S. DEPARTMENT OE AGRICULTURE. 
wound. It was also registered in the wood produced 6 to 9 feet verti- 
cally above the wound. At this point the resin passages were fewer 
than near the streak, but, nevertheless, were more numerous than in 
the round timber. The resin passages in the specimens studied were 
observed in both the open and closed condition, as is shown in the 
illustrations. Although this increased number of the resin passages, 
formed after wounding, is an important factor in securing a high 
yield, they are not, as has been shown, the only or possibly even the 
chief source of the gum. 
Provided the size of the timber and the faces and their location 
have been properly cared for, the method of chipping which is inti- 
mately connected with these features is also of fundamental sig- 
nificance. Characteristic effects on the structure of wood, result- 
ing from different methods of chipping, were determined and fully 
described in the discussion of the microscopic investigations made. 
HEAVY CHIPPING. 
Heavy chipping (more than one-half inch in height and more than 
three-fourths inch in depth) or overcupping tends to produce the 
following undesirable results in the wood formed after turpentining. 
1. Delay in the beginning of wood formation. 
2. Delay in the formation of resiniferous tissue. 
3. Reduction in width of annual rings. 
4. Reduction in amount and thickness of walls of the summer 
wood. 
5. Tendency to develop resiniferous parenchyma at the expense 
of other wood cells. 
6. Death of a relatively high percentage of trees and tendency to 
produce dry-face. 
7. Markedly reduced yield from year to year. 
CONSERVATIVE NARROW CHIPPING. 
Conservative chipping, of which the narrow, as practiced at 
Columbia, Miss., is an example, produced results in direct contrast 
to those from heavy chipping. The optimum methods of turpen- 
tining are still to be determined, but in the light of our present 
knowledge, the application of the following specifications would 
appear likely to produce the nearest approach to ideal operation that 
has thus far been attained. 
No tree under 10 inches in diameter, breast high, should be 
cupped. 
One-half, or at the very least one-third, of the total circumference 
in the neighborhood of the faces should be covered with uncut 
bark. Bark bars, at the minimum about 6 inches wide, should be 
left between faces. 
