536 Forestry Quarterly 



leaves, which in the case of most high pine land plants are tough 

 and decay slowly; so that if many years elapsed between fires 

 most of the mineral plant food near the surface might be locked 

 up in an accumulation of dead leaves, and the trees would be 

 threatened with starvation. 



"Finally, if fires should cease entirely, it is reasonably certain 

 that the high pine land vegetation would be gradually replaced 

 by that of the sandy hammocks described below. For although 

 there is little or no original or geological difference in the soil 

 of the two types, the hammock trees seem to require humus and 

 are sensitive to fire, and consequently they cannot invade the 

 pine land very fast as long as fires prevail. The Longleaf pine, 

 on the other hand, cannot stand much shade and crowding, so 

 that it cannot compete successfully with the hammock trees on 

 their own ground. At the edge of a hammock the leaves of the 

 trees must be continually falling a little way out in the pine 

 land, thus giving the humus-loving trees a chance to slowly 

 encroach on the pines." 



S. J. R. 



Strength Tests of Structural Timbers Treated by Commercial 

 Wood-Preserving Processes. By H. S. Betts and J. A. Newlin. 

 Bulletin 286, U. S. Department of Agriculture. Contribution 

 from Washington, D. C. 1915. Pp. 15. 



In this paper are presented the results of tests made by the 

 Forest Service, in cooperation with the Illinois Central Railway 

 and one eastern and two western wood-preserving companies, 

 to determine how the strength of bridge timbers is affected by 

 commercial creosote treatment. The woods used were Loblolly 

 pine, Longleaf pine, and Douglas fir. 



The results, while not conclusive in some respects, show that 

 creosote probably has no effect on the wood, but the process 

 by which the preservative is injected may cause very serious 

 weakening of the timber. The effect of a preservative process 

 on the strength of wood varies not only between different species, 

 but also within the species, depending upon the form of timber 

 used, its size, and its condition when treated. 



S. J. R. 



