OLEORESIN PRODUCTION. 
15 
the 1917 material was cut it was obvious (fig. 2) that the number of 
resin passages present by June or July in the 1917 ring was greater 
than in the 1916 ring; and at no time in 1917 was the maximum num- 
ber of resin passages in the 1916 ring as great as the maximum num- 
ber in the 1917 ring. If, on the other hand, the number of resin 
passages present in the July, 1916, material cut in 1916 (fig. 1), is 
compared with the 1917 material cut in 1917, it is apparent that 
approximately similar numbers of resin passages were present. 
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Apr. MoyJuns Jv/y Aug. Sapr. Oct: A/ok Dec. Apr May Juno Ju/y Ave. Japr Oct Nqk Dec. 
Fig. 3.— Double trees, 1916. 
Number of tracheids, observed April to 
December ; in 1916, growth ring. ° Sum- 
mer wood present. 
Number of resin centers per unit area 
(an arbitrary tangential extent ; diameter 
of microscopic field by the width of the 
annual ring observed). Observed April to 
December, 1916 ; in 1916, growing ring ; in 
1915, completed ring. 
The conclusion therefore seems justified from this and other data 
that some of the resin passages are shorter than others, and are en- 
tirely cut away as chipping progresses. The microscopic observa- 
tions indicate that in the case of the standard tract, the trees, judged 
by their wood formation in the neighborhood of the faces, a region 
where the wound response is very pronounced, did not suffer seri- 
ously from the effects of turpentining by this method for a two-year 
period. The wood formation was reduced more than in the case of 
the narrow chipping, as is brought out in the comparisons given in 
Tables 2 to 4. From Table 2, for instance, it is apparent that in 
