138 



TIMltEU PINES OF TIIK POITIIEKN UNITED STATES. 



Ill tbe limt) tlio saininorwooil is most abuiuliuit in the knot (all wood practically i)art.aking 

 of the cliaracter of suininiTWDod, at least as far as the thickness of (rell walls is concerned) and 

 in the part next to the stem, decreasinj^ with the distance from the trunk. As niij,'lit he exjiceted, 

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

 bent trunks. 



Fio. 15. — Variatinn nf siinimerwood pr-r cont with rat© of growth (width of ring), in tree No. 3, Longlraf IMnr. 

 Note.— Only tho hravy line representit Hummerwrnxl p*T cent; the others intlioat*-' the actual width of the rings (npper pair! iinil of the 

 hand of anmrnerwood (lower pair). 



GRAIN OF THK 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 fretiuently, is usually more pronounced 

 ill the basal i)ortions of the tree, and commonly varies from pith to bark in the same log. \Yavy 

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

 grain, due to the fact that the surface of the trunk for many years is (•o\ered with small, low 

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

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

 very pronounced, the tigures are somewhat obtrusive and, therefore, not fully apjjreciated. 



MINUTE ANATOMY. 



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

 of a group whose ]>osition in a general class! tication of the wood of jiines is indicated in the follow, 

 iiig scheme, suggested by Dr. J. Schroeder, and more eomiiletely by Dr. II. Mayr,' in which they 

 appear as jtart of group 2 of Section I. 



' Dr. J. Schroeder, Holz der Coniferen, Dresden, 1872, p. 65; Dr. H. Mayr, Waldungen von Nordainorika, MUn- 

 chen, 1890, p. 426. 



