. Bulletin. Forests and forestry -- United States. Fig. 11.âSpiral grain. Season checks, after re- moval of bark, indicate the direction of the fibers or grain. barK Fig. 12.âAlternating spiral grain in cypress. Side and end view of same piece. When the bark was at o the grain at this point was straight. From that time each year it grew more oblique in one direction, reaching a climax at a, and then turned back in the opposite direction. These alterna- tions were repeated periodically, the bark sharing in these changes. â in many cases the course of the fibers is spiral or twisted around
. Bulletin. Forests and forestry -- United States. Fig. 11.âSpiral grain. Season checks, after re- moval of bark, indicate the direction of the fibers or grain. barK Fig. 12.âAlternating spiral grain in cypress. Side and end view of same piece. When the bark was at o the grain at this point was straight. From that time each year it grew more oblique in one direction, reaching a climax at a, and then turned back in the opposite direction. These alterna- tions were repeated periodically, the bark sharing in these changes. â in many cases the course of the fibers is spiral or twisted around the tree as shown in fig. 11, and sometimes (commonly in butts of gum and cypress) the fibers of several layers are oblique in one direction, and those of the next series of layers are oblique in the opposite direction, as shown in fig. 12; the wood is cross or twisted grained. Wavy grain in a tangential plain as seen on the radial section is illustrated in fig. 13, which represents an extreme case observed in beech. This same form also occurs on the radial plain, causing the tangential section to appear wavy or in transverse folds. When wavy grain is fine, i. e., the folds or ridges small but numerous, it gives rise to the " curly" structure fre- quently seen in maple. Ordinarily, neither wavy, spiral, nor alternate grain is visible on the cross section; its existence often escapes the eye even on smooth, longitudinal faces in sawed material, so that the only safe guide to their discovery lies in splitting the wood in the two normal plains. Generally the surface of the wood under the bark, and therefore also that of any layer in the interior, is not uniform and smooth, but is. Fig. 13.âWavy grain in beech; after Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original United States. Divis
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