. A primer of forestry : part I, the forest. Forests and forestry. THE FOKEST. 11 and the older ones grow henceforth only in thickness (fig. 6). The fresh coat of new material mentioned above covers them year by year. There are two layers in this coat, separated by a third one of tender forming tissues called the cambium, in which the actual making of the new substance goes on. The inner side of the cambium layer forms new wood, the outer side new bark. Besides the true cambium, which forms both wood and bark, there is another cambium which makes the corky outer bark and nothing else (figs. 7
. A primer of forestry : part I, the forest. Forests and forestry. THE FOKEST. 11 and the older ones grow henceforth only in thickness (fig. 6). The fresh coat of new material mentioned above covers them year by year. There are two layers in this coat, separated by a third one of tender forming tissues called the cambium, in which the actual making of the new substance goes on. The inner side of the cambium layer forms new wood, the outer side new bark. Besides the true cambium, which forms both wood and bark, there is another cambium which makes the corky outer bark and nothing else (figs. 7 and 8). This cork cambium may encircle the whole tree, like the true cambium, as in the. Fig. 8.—Outer surface of bark of the Western Yellow Pine, showing the scales made by the successive layers of cork cambium. Red Cedar, or it may form little separate films in the bark, but in either case it dies from time to time, and is re-formed nearer the wood. THE STRUCTURE OF WOOD. Wood is chiefly made up of very small tubes or cells (fig. 9) of vari- ous kinds, which have special uses in the life of the tree. Some con- duct water from the roots to the crown, some store away digested food, and others merely strengthen the structure of the wood and hold it together. The wood of cone-bearing or coniferous trees (like the pines and spruces) has but few kinds of cells, while that of the broad- leaf trees (such as oaks and maples) is much less simple. But in each case some of the cells have thick walls and small openings, and others wide openings and very thin walls. In climates which have regularly one season of growth and one of rest, like our own, the cells of the 173. 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 Pinchot, Gifford, 1865-1946. Washington, D. C. : U. S. Dept. of Agriculture
Size: 1657px × 1508px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectforestsandforestry
