. An introduction to vegetable physiology. Plant physiology. THE SKELETON-OF THE PLANT 55 exterior and the metabolic tissue of the cortex of stems, thus cutting off the intercellular space system of the latter from access to the air, they are usually penetrated by special structures known as lenticels. These are made up of corky cells very loosely arranged, and consequently set up the communication needed (fig. 47). During the winter a layer of cork is formed below the lenticel. In the corky cell-wall the cutin is frequently associated with a certain amount of Ugnin. The thin corky walls posse
. An introduction to vegetable physiology. Plant physiology. THE SKELETON-OF THE PLANT 55 exterior and the metabolic tissue of the cortex of stems, thus cutting off the intercellular space system of the latter from access to the air, they are usually penetrated by special structures known as lenticels. These are made up of corky cells very loosely arranged, and consequently set up the communication needed (fig. 47). During the winter a layer of cork is formed below the lenticel. In the corky cell-wall the cutin is frequently associated with a certain amount of Ugnin. The thin corky walls possess almost exactly the same physical properties as the thickened cuticle of the epidermis, a fact which affords evidence that the primary function of both is the Ficf. 46.—Outer Portion of Cortex OF YoimG Twig ot Lime. per, cork layer; ^h, meristem layer. Fig. 47.—Section of a Lenticel. /, lenticel; per, cork layer. Like the substance of the' middle lamella, both Hgnin and cutin are soluble in warm nitric acid containing potassic chlorate. In some cases the cell-walls of the epidermal protoplasts are impregnated with various matters that do not proceed from their own disintegration. Among these are various fatty bodies, while wax is sometimes very conspicuous. The bloom of such fruits as the grape and the plum is composed of very fine waxy particles ; the impregnation in their case having been so great that certain particles have passed beyond the walls and formed a layer on the outer surface. The leaves of the wax-palm show an even denser deposit. Mineral matters are also of frequent occurrence in the. 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 Green, J. Reynolds (Joseph Reynolds), 1848-1914. London, J. & A. Churchill
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