. Bulletin. Forests and forestry -- United States. 18 TIMBER. removal of the bark from a fresh piece of white pine, cut in winter, where they appear as conspicuous white lines, extending often for many inches up and down the stem. Neither the horizontal nor the vertical resin ducts are vessels or cells, but are openings between cells, i. e., intercellular spaces, in which the resin accumulates, freely oozing out when the ducts of a fresh piece of sapwood are cut. They are present only in our coniferous woods, and even here they are restricted to pine, spruce, and larch, and are normally ab- se
. Bulletin. Forests and forestry -- United States. 18 TIMBER. removal of the bark from a fresh piece of white pine, cut in winter, where they appear as conspicuous white lines, extending often for many inches up and down the stem. Neither the horizontal nor the vertical resin ducts are vessels or cells, but are openings between cells, i. e., intercellular spaces, in which the resin accumulates, freely oozing out when the ducts of a fresh piece of sapwood are cut. They are present only in our coniferous woods, and even here they are restricted to pine, spruce, and larch, and are normally ab- sent in fir, cedar, cypress, and yew. Altogether the structure of coniferous wood is very simple and regular, the bulk being made up of the small fibers called tracheids, the dis- turbing elements of pith rays and resin ducts being insignificant, and hence the great uniform- ity and great technical value of coniferous Fig. of oak. C. S., cross section; R. S., radial sec- tion ; T. 8., tangential section; m. r., medullary or pith ray; a, height, b, width, and e, length of a pith ray. "WOOD OF BROAD-LEAVED TREES. On a cross section of oak, the same arrangement of pith and bark, of sapwood and heartwood, mmm m ¥ m\\\ 1 iiPA and the same disposition of the wood in well-defined con- centric or annual rings occurs, but the rings are marked by lines, or rows, of conspicuous pores or openings which oc- cupy the greater part of the spring wood of each ring (see fig. 6, also fig. 8) and are, in fact, the hollows of vessels through which the cut has been made. On the radial sec- tion, or quarter-sawed board, the several layers appear as so many parallel stripes (see fig. 7); on the tangential section or "bastard" face, patterns similar to those men- tioned for pine wood are ob- served. But while the pat- terns in hard pine are marked by the darker summer wood and are composed of plain, alternating stripes of darker and lighter wood, the figures in oak (and ot
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