. American forestry. Forests and forestry. JPr^.d. cells of a group. Seen in a longitudinal section, the canal that is filled with resin appears to have been formed by the absorption of the walls of resin cells. Such sections show that resin canals are not continuous, but that there are places where the cross-walls have not been wholly absorbed. Twigs from five to ten years old are best for studying the development of resin canals, because in older wood they are already fully developed. If the canals consist simply of wide central cells, such elements may be seen either in their original form
. American forestry. Forests and forestry. JPr^.d. cells of a group. Seen in a longitudinal section, the canal that is filled with resin appears to have been formed by the absorption of the walls of resin cells. Such sections show that resin canals are not continuous, but that there are places where the cross-walls have not been wholly absorbed. Twigs from five to ten years old are best for studying the development of resin canals, because in older wood they are already fully developed. If the canals consist simply of wide central cells, such elements may be seen either in their original form or with their cross-walls perforated or totally absorbed. In this stage the side-walls have undergone very little change, and the canal merely consists of one or more rows of cells. stc. grains of starch. After growth has started in early spring the starch grad- ually disappears, and the cells become filled with a fluid mass which is later transformed into a yellowish or reddish- colored resin. The resin gradually hardens and forms an inner layer or oc- casionally fills the entire cavity. Longi- tudinal sections of young twigs show perpendicular rows of wood-paren- chyma fibers that contain starch grains in the uppermost cells, while the lowermost ones contain starch and resin or resin only. The starch grains which originally filled the cell cavities. 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 American Forestry Association. Washington, D. C. : American Forestry Association
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectforestsandforestry
