. American forestry. Forests and forestry. 354 AMERICAN FORESTRY Resin canals in white fir occur in small groups of two to six or more in the early-wood, and usually near the inner boundary of concentric zones (Figs. 5 and 6). These canals are al- ways in direct communication with pith rays (Figs. 5A, •5B, and 6), and are surrounded by wood-parenchyma fibers that contain starch during the winter (Figs. 5 and 6 st. g.). Transverse sec- tions of twigs cut from the top of the tree show resin canals con- sist of compact groups of cells, the cen- tral portions of which are composed of. n
. American forestry. Forests and forestry. 354 AMERICAN FORESTRY Resin canals in white fir occur in small groups of two to six or more in the early-wood, and usually near the inner boundary of concentric zones (Figs. 5 and 6). These canals are al- ways in direct communication with pith rays (Figs. 5A, •5B, and 6), and are surrounded by wood-parenchyma fibers that contain starch during the winter (Figs. 5 and 6 st. g.). Transverse sec- tions of twigs cut from the top of the tree show resin canals con- sist of compact groups of cells, the cen- tral portions of which are composed of. numerous round cells with wide cell cavities, but in other respects are simi- lar to the cells that are filled with starch during the winter (Fig. 7). In the early spring, when the vegetable pe- riod begins, the starch is replaced by a volatile oil, and during the first win- ter there is no trace of resin in these cells. Longitudinal sections show that resin passages are surrounded by wood- parenchyma fibers, the cells of which are from two to three times as long as those in the center of the group. In other respects the inner and outer rows of cells are similar. The pits are sim- ple, and only where resin cells touch tracheids do they appear to be bor- dered; such borders are always within. 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
Size: 1155px × 2163px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectforestsandforestry
