. Botany; principles and problems. Botany. 96 BOTANY: PRINCIPLES AND PROBLEMS Protective Layers.—The epidermal cells resemble those of the leaf epidermis and require no special comment. In stems which are growing in thickness, however, the epidermis is soon sloughed off and its protective function is assumed by a layer of corky cells formed directly under it and constantly renewed. In these cells the protoplasm soon disappears and the normal. Fig. 48.—Tranfe\ei-5e section of a thicc-\ c ii-oUl twig of the tiilip-tree {Lirio- dendron). This is a t>pical wood> twig The hbro-vascular cylind
. Botany; principles and problems. Botany. 96 BOTANY: PRINCIPLES AND PROBLEMS Protective Layers.—The epidermal cells resemble those of the leaf epidermis and require no special comment. In stems which are growing in thickness, however, the epidermis is soon sloughed off and its protective function is assumed by a layer of corky cells formed directly under it and constantly renewed. In these cells the protoplasm soon disappears and the normal. Fig. 48.—Tranfe\ei-5e section of a thicc-\ c ii-oUl twig of the tiilip-tree {Lirio- dendron). This is a t>pical wood> twig The hbro-vascular cylinder consists of a solid ring of wood within and ba^t without, surrounding a central pith. cellulose wall becomes corky or suherized and is thus rendered almost impermeable to air or water. The lenticels, which we have already mentioned, are spots in this corky layer where the cells are somewhat loose and spongy and thus allow the passage of gases. Cortex and Pith.—The cortex and the pith are very similar in constitution. Their cells usually remain alive, are roughly spherical in shape, retain their cellulose walls and function chiefly in the storage of food. To such undifferentiated tissues the term parenchyma is often applied. In older woody stems the pith often dries up and collapses; and the cortex, crushed by the expansion of the wood underneath it, is finally sloughed 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 Sinnott, Edmund Ware, 1888-. New York, McGraw-Hill
Size: 1302px × 1919px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, booksubjectbotany, bookyear1923
