. Identification of the economic woods of the United States : including a discussion of the structural and physical properties of wood . Wood; Trees. ECONOMIC "WOODS OF THE UNITED STATES 27 rays in Sassafras are much more distinct than in Fraxinus; like- wise in Celtis and Ulmus, Tilia and /Esculus, Acer and Betula. In white oaks the height of the large rays averages considerably greater than in the red or live oaks. In dicotyledonous species the rays are composed wholly of parenchyma. In certain Gymnosperms {Pinus, Larix, Picea, Pseudotsuga, Tsuga, and occasionally in others) ray trachei
. Identification of the economic woods of the United States : including a discussion of the structural and physical properties of wood . Wood; Trees. ECONOMIC "WOODS OF THE UNITED STATES 27 rays in Sassafras are much more distinct than in Fraxinus; like- wise in Celtis and Ulmus, Tilia and /Esculus, Acer and Betula. In white oaks the height of the large rays averages considerably greater than in the red or live oaks. In dicotyledonous species the rays are composed wholly of parenchyma. In certain Gymnosperms {Pinus, Larix, Picea, Pseudotsuga, Tsuga, and occasionally in others) ray tracheids are present (Figs. 4-7). They are usually marginal, but often inter- spersed and sometimes they compose entire rays, particularly. Fig. 6.—Radial section of a ray of Pinus resinosa (red or Norway pine), showing the dentations (d) or reticulations on the upper and lower walls of the ray tracheids (r. tr.), and the presence in the lateral walls of the ray-parenchyma cells (r. p.), of large simple pits (s. p.) communicating with the wood tracheids (w. tr.) adjacent; h. p., bordered pit. Magnified about 250 diameters. low ones. They can be distinguished from the ray-parenchyma cells by the presence of bordered pits in the lateral and especially the end walls. They are often irregular in outline and are devoid of visible contents. They have their counterparts in the paren- chymatous tracheids surrounding the epithelial cells of resin cysts and ducts. In the young root, and sometimes in the young stem as well, special upright or oblique forms occur which may be considered as transitional from wood tracheids to ray tracheids. The character of the upper and lower walls of the ray tracheids, whether smooth, as in soft pines, or dentate or reticulate, as in. 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 R
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Keywords: ., bo, bookcentury1900, bookdecade1910, booksubjectwood, bookyear1912
