OLEORESUST 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 lias 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 

 -timulu- i given. Qleoresin exudes from the rcsiniferous paren- 

 chyma prc.-cnf. Tf tend- to coat the surface and to cover it with a 



more or !<• .- - complete seal, which materially assists in preventing 

 tie- drying out of the exposed sap wood. Probably mo-l of the Daren 



chyma cells close to the surface of the wound, e-pecially those actu- 

 ally <-i)t. may die. The wound stimulus is undoubtedly grcalesl in 

 the immediate vicinity of (he wound. Its effect appear- to he mani 



