148 



TIMBER PINES OF THE SOUTHERN UNITED STATES. 



Iii the limb the smmnerwood is most abundant in the knot (all wood practically partaking 

 of the character of snmnitTwood, at least as far as the 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 the underside of limbs and the concave portions of 

 bent trunks. 



S 9 10 11 12 13 14 15 16 



Decades of Rings Trom, periphery 



FIG. 15 Variation of summerwood per cent with rote of growth (width of ring), in tree No. 3, Longleaf Pine. 



KOTK Only the heavy line represents nuinmerwood per cent; the others indicate the actual width of the rings (upper pair) and of th 



hand of summerwood (lower pair). 



GRAIN OF THE WOOD. 



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

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

 in the 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 pronounced, the 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 

 ot a group whose position in a general classification of the wood of pines is indicated in the follow, 

 ing scheme, suggested by Dr. J. Schroeder, and more completely by Dr. H. Mayr, 1 in which they 

 appear as part of group 2 of Section I. 



1 Dr. J. Schroeder, Holz der Coniferen, Dresden, 1872, p. 65; Dr. H. Mayr, Waldungen von Nordarnerika, Mtin- 

 chen, 1890, p. 426. 



