138 



TIMBER PINES OF THE SOUTHERN UNITED STATES. 



Ill the limb the summorwooil is most abundant in the knot (all wood practically jtartaldng 

 of the character of summcrwood, at least as far as the thickness of cell walls is concerned) and 

 in the i)art next to the stcsm, decreasing with the distance from the trunk. As might be expected 

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

 bent trunks. 



i.f the 



Fia. 15 — Variation c.f siiinmerwood per cent with rate of growth (width of ring), in tree No. 3, Longlcnf Tine. 

 Note.— Only the heavy lino rc|irC8(-nts minimerwood per cent; the otli.rs indicate tlie artnal width of the rinf;s (upper imir) and 

 hand of sunimerwood (h>wiT pair). 



GKAIN OF THK "WOOU. 



Though usually (piite stiaiglit grained, the wood of these species is by no means always so. 

 Sjnral growth leading to " (rossgraiiicd " lumber occurs frequently, is usually more pronounced 

 in the basal i)ortions of the tree, and ((immonly varies from pith to bark in the same log. Wavy 

 grain resembling that of (he maple (curly mai)le) lias not been observed, but an irregular wavy 

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

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

 remarkably pretty patterns. Unfortunately the contrast of spring and suiiiiiicr wooil being so 

 very pronounced, the (igures are somewhat obtrusive and, therefore, not fully ai)preciated. 



MINUTE ANATOMY. 



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

 of a group who.se position in a geiieial classiiication of the wood of ])incs is indicated in the follow, 

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

 appear as partof grou]) '1 of Section I. 



> Or. .1. Schroodor, Holz dor Coniferoii, Dresden, 1872, p. (S; Dr. H. Mayr, Waldungen von Nordamorika, Mliu- 

 cbeu, 1890, p. 420. 



