. A manual of the North American gymnosperms [microform] : exclusive of the cycadales but together with certain exotic species. Bois; Trees; Gymnosperms; Gymnospermes; Arbres; Wood. 328 ANATOMY OF THE GYMNOSPERMS 6. * • S. Pentaallowii, JefiFtey " Tranmerse. Rings of growth rather narrow, with sharply marked but thin summer wood. Rings regular, or if varying in thickness, varying uni- formly and without violent transitions except as the result of injury. Resin canals present in both the vertical and horizontal planes appar- ently only as the result of injury. The resin canals when present
. A manual of the North American gymnosperms [microform] : exclusive of the cycadales but together with certain exotic species. Bois; Trees; Gymnosperms; Gymnospermes; Arbres; Wood. 328 ANATOMY OF THE GYMNOSPERMS 6. * • S. Pentaallowii, JefiFtey " Tranmerse. Rings of growth rather narrow, with sharply marked but thin summer wood. Rings regular, or if varying in thickness, varying uni- formly and without violent transitions except as the result of injury. Resin canals present in both the vertical and horizontal planes appar- ently only as the result of injury. The resin canals when present surrounded by resin cells, containing dark brown resin. Resin cells inconspicuous and confined to the face of the summer wood, except in the case of injury, where they may be present throughout the zone of annual growth. Tracheids of the spring wood very large and with pits on the radial walls only. of the summer wood with tangential ; " Radial. Rays without tracheidal cells, but with distinctly differentiated marginal cells. Lateral pits of the ray cells elliptical, bordered, larger in the marginal cells. Rows of pits single in the central cells of the ray and 2-3 seriate in the marginal cells. Medullary ray cells covering 1-4 tracheids, the central ones resiniferous, the marginal generally empty, sometimes containing large clinorhombic crystals inclosed in cysts derived from the cell walls. Marginal cells with undulating free border, deeper than central cells. End walls of the cells of the medul- lary rays very strongly pitted. Longitudinal walls of ray cells also pitted and rather thick. Rays contain resin canals in the case of injury, which take their origin from similar vertical canals running in the wood. Resin canals of the rays sometimes ending blindly and sometimes in a more external series of vertical canals, often extending through many annual rings, varying greatly in size and frequently occluded by thyloses. Spring tracheids generally wi
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