1390 A NATIONAL PLAN FOR AMERICAN FORESTRY 



it appears that reduction in strength may occur when the rate of 

 growth is slowed down by crowding of the stand. Thus some of the 

 most readily controlled growth conditions are found to have important 

 effects on wood properties. 



The effects of growth conditions are brought about through the 

 physiological processes of the tree, which must be much better under- 

 stood in order to lay a proper scientific foundation for further work. 

 The source and nature of the food supply, its elaboration into inter- 

 mediate and final products, its translocation to point of final use, the 

 transpiration process, storage of reserve materials, and moisture 

 and temperature limitations are some of the important physiological 

 factors about which the existing information is fragmentary. 



The special physiological processes involved in resin formation are 

 of great importance in connection with the production of turpentine 

 and rosin from longleaf and slash pines. Research on the develop- 

 ment of the resin ducts in response to the wounding of the tree has 

 already assisted in improving chipping methods so that better yields 

 can be obtained with less injury to the tree. Further improvements 

 depend on more detailed knowledge of the physiology of resin 

 formation. 



WOOD-DESTROYING ORGANISMS 



There is another type of fundamental research that is not con- 

 cerned directly with wood but instead with the various organisms 

 that attack wood under certain conditions of its use. The three 

 principal groups of such wood-destroying organisms are the fungi, 

 the insects, and the marine borers. The fungi are responsible for the 

 well-known decay and staining of wood, while insects and marine 

 borers destroy wood in the course of using it for both food and shelter. 

 Further improvements in methods of protection against these organ- 

 isms require a fuller knowledge of their life history and habits, and 

 especially of the conditions favorable and unfavorable to their attacks 

 on wood. It is known, for instance, that wood may be too wet or 

 too dry for wood-destroying fungi to attack it, but the limits of 

 moisture control between which they are active are not known with 

 any accuracy. 



Such fundamental biological research may have fairly direct prac- 

 tical application, since many if not most of the difficulties with these 

 organisms are caused by faulty practice in cutting, manufacture, or 

 storage of the wood or in the design or condition of use of the final 

 product faulty practice that can frequently be improved or per- 

 fected simply and cheaply when there is sufficient knowledge of the 

 limitations of the organisms. Biological research is especially import- 

 ant with fungi, because of the multitude of species that attack wood 

 and the great variation in their characteristics. 



Biological research on wood-destroying organisms may also be of 

 value for the purpose of producing chemicals from wood. Molds 

 and bacteria have been recently found that under controlled conditions 

 produce acetic acid, lactic acid, ethyl alcohol, and other higher acids 

 and alcohols from cellulose, and it is possible that similar products 

 could be thus obtained from wood cellulose or direct from wood. 

 Certain organisms attack lignin but, so far as it is now known, 

 without forming useful products. 



