. Wood and forest . owI ^ thru tliem. It loses its V jirotoplasm anr] starch and becomes heart-wood, in which allcells are dead andserve only the me-chanical function ofholding up the greatweight of the tree andin resisting wind pres-sures. This is the rea-son Mdiy a tree mayhctome decayed andlioUow and yet be aliveand liear fruit. In atree that is actuallydead the sap-wood rotsliist. Chemical s it b-stances infiltrate intothe cell walls of heart-wood and hence it has a darker color than the sap-wood. Persimmonturns black, walnut purplish brown, sumac yellow, oak light brown,tulip and poplar y
. Wood and forest . owI ^ thru tliem. It loses its V jirotoplasm anr] starch and becomes heart-wood, in which allcells are dead andserve only the me-chanical function ofholding up the greatweight of the tree andin resisting wind pres-sures. This is the rea-son Mdiy a tree mayhctome decayed andlioUow and yet be aliveand liear fruit. In atree that is actuallydead the sap-wood rotsliist. Chemical s it b-stances infiltrate intothe cell walls of heart-wood and hence it has a darker color than the sap-wood. Persimmonturns black, walnut purplish brown, sumac yellow, oak light brown,tulip and poplar yidlowisli, redwood and eedar brownish red. Manv•\ioods, as mahogany and oak, darken under exposure, which showsthat the substances producing the color are oxidizable and unstable.^ d\es are obtained by boiling and distilling such woods as su-mach, logwood, red sanders, and fustic. Many woods also acquiredistinct odors, as camplior, sandalwood, cedar, cypress, pine andmahogany, indicating the presence of Fig-. S. Section of Dou^-las Fir, Sliowinrr Aniiual Rings and Knois al Cemer of Trunk. Anuricair Musiiim of Natui-al Utslory, X. }. THE STRUCTURE OF WOOD. 19 As a rule heart-wood is more valuable for timber, being harder,heavier, and drier than sap-wood. In woods like hickory and ash,howevei, which are used for purposes that require pliability, as inbaskets, or elasticity as in handles of rakes and hoes, sap-wood ismore valuable than heart-wood. In a transverse section of a conifer, for example Douglas S. the wood is seen to lie in concentric rings, the outer part ofthe ring being darker in color than the inner part. In reality eachof these rings is a .section of an irregular hollow cone, each cone en-veloping its inner ncighlior. Each cone ordinarilyconstitutes a years groi\tli, and therefore thereis a greater number of tliem at the liase of a treethan higher up. These cones vary greatly in//nV/rH(.!-■,?. or, looking at a cross-section, tlie ringsvar
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectforests, bookyear1912
