OLEORESIN PRODUCTION. 39 
of chipping advisable in relation to the width of the sapwood. More 
information, in addition to the results obtained in the Florida 
National Forest experiments, is desirable in regard to the relative 
width of face to employ. Which, for instance, is more costly, and 
which produces higher yields, the use of two small faces or of one 
large one, or, on larger trees, two large faces or three small ones? 
In this connection it is important to determine under what cir- 
cumstances the peak is kept most healthy and productive, since it is 
at the peak that dry-facing most often begins. The question of the 
minimum width of bark bars between faces is fairly well determined, 
but an innovation in the form of leaving a bark bar in the middle 
of the face, which is practically equivalent to chipping two small 
faces, has been suggested. 
A detailed study of the length of the normal resin passages and of 
those formed after wounding, made by dissecting the outer sur- 
faces of logs, would furnish information bearing on the desirable 
height of chipping, and on the matter of maintaining gum produc- 
tion, at least at the level of that obtained during the first year of the 
operation. 
The effect on yields of resting the timber for a year or for a 
shorter period of weeks or months at some time during the operation 
might be significant. In one instance it is reported that timber tur- 
pentined for two years and rested for a year before continuing the 
operation gave exceptionally high yields. 
More exact information regarding the responses associated with 
the use of the advance streak is essential in order that this practice 
should be more fully understood. 
The method of using closed cups made it possible to obtain a very 
high grade of gum, which gave an exceptionally high yield of tur- 
pentine, but it was impractical in operation because of the difficulties 
encountered in freshening the yielding surface and because of the 
expense of the cups. It seems possible, nevertheless, that some method 
of covering the cups, such as is used in India, or of protecting the 
faces or of using borings instead of open faces, 38 might be devised. 
By such means evaporation might be markedly reduced and produc- 
tion notably increased. 
It is highly desirable that some of the conclusions recently obtained 
in German experiments 39 should be checked upon American species. 
The filling and the emptying of the resin passages during turpentin- 
ing is a problem of fundamental significance. The steps in the proc- 
ess by which the tree manufactures the oleoresin are still practically 
83 " To try out the Augur and Glass Holder System." Naval Stores Review, 31 : June 
25, 1921, p. 10. 
39 Munch, E. : " Naturwissenschaftliche Grundlagen der Kiefernharznutzung." Arbeiten 
a. d. Biol. Reichsanstalt fiir Land-u. Forstwirts. 10 Bd. : 1919. 
