OLEORESIN PRODUCTION. 
23 
Production of resiniferous tissue. — Many more resin passages than 
are normally present were formed in the wood which developed after 
wounding. (Figs. 5 and 6.) 
In both the 1916 and 1917 rings the greatest number of resin 
passages per unit area was present in the specimens from the narrow- 
chipped trees, although the average number present in the 1915 
ring, when the timber had not been turpentined, chanced to be smaller 
(Table 4) than in the case of either the standard or the double 
specimens. In 1916 the earliest formation of resin passages was 
also found in the narrow-tract specimens. 
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Mor Apr Moy JurtzJo/y Aug. Sepr. Oct. Ator. Mar Apr. May June. Ju/y Auo. 5apt Oct No* 
Fig. 6. — Narrow trees, 1917. 
Number of tracheids, observed March to 
November ; in 1917, 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 March to 
November, 1917; in 1915, 1916, and 1917, 
growth rings. , 1915 ; , 1916 ; , 
1917. 
At the level of the 1917 chipping, fewer resin passages per unit 
area were present in the 1916 rings than at the lower levels, judging 
the latter from the specimens studied during their development in 
the 1916 growing season. This was also true in the other two 
methods practiced. Some, but not all, of the resin passages induced 
by wounding were therefore apparently relatively short and appear 
to have been cut away as chipping progressed up the tree. 
The largest resin passages found in the narrow material collected 
in 1917 were present in the 1916 ring, which was produced during 
the first year of turpentining. The year 1916 was found, further- 
