148 



TIMBER PINES OF THE SOUTHERN UNITED STATES. 



In the limb tbe summerwood is most abundant in the knot (all wood practically partaking- 

 of the cbara(!ter of summerwood, at least as far as tbe thickness of cell walls is concerned) and 

 in the part next to the stem, decreasing with the distance from the trunk. As might be expected, 

 it also forms a larger per cent of the wood of tbe underside of limbs and the concave portions of 

 bent trunks. 



Fig. 15.— Variation of summerwood i>er cent with rate of growth (width of rius), in tree Xo. 3, Loiigk-.if rinc. 

 Note — Only the heavj- line represents summerwood per cent; the others indicate the actual width of the rin;.'s (ni.|i.i i.Mir. and ..i' ilie 

 It.Tnd of summerwood {lower pair). 



GRAIN OF THE ^VOOD. 



Tliough usually quite straight grained, tbe wood of these species is by no means always so. 

 Spiral growth leading to "cross-grained" lumber occurs frequently, is usually more ijronouuced 

 in tbe basal portions of the tree, and commonly varies from pith to bark in the same log. Wavy 

 grain resembling that of the maple (curly maple) has not been observed, but an irregular wavy 

 grain, due to the fact that the surface of the trunk for many years is covered with small, low 

 eminences, 1 to a few inches across, is frequently seen, especially in Longleaf Pine, and leads to 

 remarkably pretty patterns. Unfortunately the contrast of spring and summer wood being so 

 very ijronouuced, tbe figures are somewhat obtrusive, and, therefore, not fully appreciated. 



MINUTE ANATOMY. 



The minute structure or histology of the wood of the five species under consideration is that 

 of a group whose position in a general classifi(;ation of the wood of pines is indicated in the follow- 

 ing scheme, suggested by Dr. J. Schroeder, and more completely by Dr. H. Mayr,' in which they 

 appear as jjart of group 2 of Section I. 



' Dr. J. Schroetlcr, Holz tier Couiferen, Dresden, 

 cben, 1890, \^. 426. 



p. 65; Dr. II. Mayr, Waldiiugeu von Nordanierik.i 



