OLEORESIN PRODUCTION. 31 
trees was also considerably richer in turpentine than the ordinary 
dip, and fewer dry faces and dead trees were found on these crops. 
In conclusion, therefore, it may be said that these early Forest 
Service experiments clearly showed the advantages of certain con- 
servative turpentining methods, which as was at that time felt, were 
only an indication of what might be accomplished in this direction. 
CHIPPING IN THE LIGHTWOOD. 
There is a belief current among practical turpentine operators 
• that, to obtain the best yields from turpentining a substantial amount 
of wood, a high chip should be cut away each week in order to 
" keep ahead of the lightwood." By lightwood is meant the region 
above the streak which is more or less saturated with oleoresin. The 
presence of lightwood is indicated by the difference in color be- 
tween the surface of the freshly cut streak and that of a wound 
newly cut in round timber. It may be that the wood is only slightly 
impregnated with resin, so that the summer wood bands appear 
somewhat darker than normally, or, on the other hand, that a con- 
siderable amount of resin may have soaked into the wood, markedly 
darkening it, and often making the summer wood appear translucent, 
especially when the light is allowed to shine through a chip from 
such a region. An extreme example of this is shown in Plate III, 
figure 1, in which case the saturation probably occurred as a result 
of the undue drying out and dying of the overstimulated tree. 
Narrow chipping, one- fourth inch to a strict one-half inch in 
height, will not keep ahead of all lightwood, especially during the 
midsummer season. For this reason many practical operators were 
convinced in advance that narrow chipping would fail. However, 
as has been shown, the results of reducing the height of the chipping 
speak for themselves in terms of increased yields and sustained vi- 
tality of the trees, as indicated, for instance, by the late autumn re- 
sponse shown in Plate III, figure 2, and by the recovery of the tree 
under turpentining, shown by the amount of wood formation in 
Plate V, figures 3 and 4. 
The following interpretation of the observations made appears to 
be justified by the results obtained. When a tree is chipped or scari- 
fied the living cells in the wood are injured and a strong wound 
stimulus is given. Oleoresin exudes from the resiniferous paren- 
chyma present. It tends to coat the surface and to cover it with a 
more or less complete seal, which materially assists in preventing 
the drying out of the exposed sapwood. Probably most of the paren- 
chyma cells close to the surface of the wound, especially those actu- 
ally cut, may die. The wound stimulus is undoubtedly greatest in 
the immediate vicinity of the wound. Its effect appears to be mani- 
