Title: (Bulletins on forest pathology : from Bulletin U.S.D.A., Washington, D.C., 1913-1925)
Identifier: bulletinsonfores00unit (find matches)
Year: 1913 (1910s)
Authors: United States. Dept. of Agriculture
Subjects: Trees; Plant diseases
Publisher: (Washington : U. S. Dept. of Agriculture)
Contributing Library: Robarts - University of Toronto
Digitizing Sponsor: University of Toronto

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DECAYS AND DISCOLORATIONS IN AIRPLANE WOODS. 21 shaped areas, which on the tangential or slash-grain face and the radial or edge-grain face of a board appear as brown streaks, usually running in a vertical direction. (Figs. 8 and 9.) The wood for a little distance around a pith-ray fleck may be darker than normal. This is particularly so in poplars or cottonwoods (Populus spp.). On the whole, the injuries are not at all serious, having no noticeable effect on the strength of the wood unless the flecks are exceedingly
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Fig. 7.—Slash-grain or tangential surface of a tulip-poplar board, showing stain and bird's-eye caused by sapsuckers. One-third natural size. (Courtesy of the U. S. Biological Survey.) numerous. Only in the cherries (Prunus spp.) may a weakening be expected, for there the affected wood tissues are broken down, while in the other woods they are but little distorted. Furthermore, the presence of pith-ray flecks is usually hard to detect in the heart- wood of cherries. The color of the heartwood differs but little from the color of the pith-ray flecks. Pith-ray flecks are found in all the common poplars or cotton- woods, birches, maples, cherries, basswood, and many others, but there is considerable variation in their abundance on different closely related species. For example, these flecks are ver)7 common in soft maple, while they are rather infrequent in hard maple. In river, gray, and paper birch (Betula nigra Linn., B. populifolia Marsh, and B. papyrifera Marsh) they are found in abundance, but are

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