50 



THE COMMERCIAL HICKORIES. 



HEARTWOOD AND SAPWOOD. 



In the case of the hickories there is an unfounded prejudice against 

 the heartwood. Specifications place white hickory, or sapwood, in 

 a higher grade than red hickory, or heartwood, though there is no 

 inherent difference in strength. In fact, in the case of large and old 

 hickory trees the sapwood nearest the bark is comparatively weak, 

 and the best wood is in the heart, though in young trees of thrifty 

 growth the best wood is in the sap. 



TABLE 16. Comparative values of sapwood and heartwood in selected pieces of green 

 pignut and shaybork, and in commercial hickories taken at random. 



Table 16 gives the results of tests from selected pieces lying side 

 by side in the same tree, and also the average values for heart- 

 wood and sapwood in shipments of the commercial hickories without 

 selection. It shows conclusively that the transformation of sapwood 

 into heartwood does not affect either the strength or toughness of the 

 wood. This conclusion is also confirmed by Forest Service Circular 

 142, which shows that, weight for weight, sound hickory is equally 

 strong, regardless of color. Therefore the user of hickory should not 

 discriminate against heartwood in buying stock. It is true, how- 

 ever, that sapwood usually is more free from latent defects than 

 heartwood. 



POSITION IN THE TREE. 



The determination of the strength of material at various distances 

 from the center of the tree toward the bark gives a good- indication 

 of the effect of growth on strength. In trees from forests which have 

 grown for a long time under fixed conditions it is necessary only to 

 take a specimen from a predetermined point in the cross section at a 

 given height to determine a factor which represents the mechanical 



