40 BULLETIN 1064, U. S. DEPARTMENT OF AGRICULTURE. 



unknown. A more intimate knowledge of the substances of the great- 

 est significance in resin production — as, for instance, the effects of the 

 constitution of the soil — might have a marked influence on future 

 practice. This has been found to be the case with fruit culture, as a 

 result of the work on the effects of the carbon-nitrogen ratio upon 

 vegetative and reproductive responses. 40 Indeed, as has been sug- 

 gested by Dr. W. D. Bancroft, chairman of the division of chemistry 

 and chemical technology of the National Research Council, who 

 selected oleoresin production as an example of an important present- 

 day problem, the understanding of this subject appears to involve 

 cooperative work by a botanist, a microscopist, an organic chemist, 

 and a colloid chemist. Much valuable information on oleoresin has 

 already been collected by the Bureau of Chemistry and by different 

 units of the Forest Service, and with the timber on the Florida Na- 

 tional Forest available for experiment, the opportunities for carrying 

 on further research are exceptionally good. That the future need in 

 this direction is recognized and that plans (in the carrying out of 

 which microscopically obtained data can unquestionably be of serv- 

 ice) are being formulated, is indicated in the following statement of 

 Col. W. G. Greeley, Forester : 41 



One of the things which must be worked out as part of our general progress 

 in forest conservation is a system of extracting gum turpentine which will make 

 this industry and its valuable commercial products a permanent resource of 

 the Southern States. We must develop a plan for tapping second-growth timber, 

 somewhat along the lines used in France but adapted to commercial require- 

 ments in the United States, under which this can be a continuous forest indus- 

 try, obtaining yields of gum from the same trees for 20 or 30 years, right up 

 to the time when they are cut and converted into lumber. Without some 

 method of this nature the gum turpentine industry will soon cease to exist. 

 I am hopeful that the Forest Service can extend the instructive experiments in 

 various methods of conservative chipping and cupping which you 42 have already 

 initiated on . the Florida National Forest in order to work out completely a 

 plan of tapping second-growth timber without injury which can be adopted 

 commercially by the owners of pine land throughout the South. 



SUMMARY. 



The results of this work and of the other earlier and current ex- 

 periments of the Forest Service clearly demonstrate that those 

 methods which conserve the vitality of the tree and its responsive 

 power, under stimulation such as is given by turpentining, insure 

 the greatest production of oleoresin. The process of turpentining 

 is not merely a draining out of the gum already formed ; it is a col- 

 lection of the oleoresin constantly being manufactured by the tree. 



40 Kraus, E. J., and H. R. Kraybill, Oregon Agric. College, Exper. Station. Bulletin 149, 

 1918. 



41 For. Serv. Bui., Jan. 3, 1921. 



43 That is, Florida National Forest organization. 



