. An introduction to vegetable physiology. Plant physiology. THE STORAGE OF EESEEVE MATEEIALS 225 growth in thickness of the trunk or root is stopped. Cell- division is indeed the result of cell-growth. When a cell of the cambium has attained its full size it divides into two, each of which then grows to its appropriate adult dimensions; some divide again, like those from which they sprang ; others become transformed into wood or bast cells. In either case an immediate supply of food is needed, and from the condition of things this must be near at hand. The stream from the leaves is inter- mit
. An introduction to vegetable physiology. Plant physiology. THE STORAGE OF EESEEVE MATEEIALS 225 growth in thickness of the trunk or root is stopped. Cell- division is indeed the result of cell-growth. When a cell of the cambium has attained its full size it divides into two, each of which then grows to its appropriate adult dimensions; some divide again, like those from which they sprang ; others become transformed into wood or bast cells. In either case an immediate supply of food is needed, and from the condition of things this must be near at hand. The stream from the leaves is inter- mittent, and hence it is important that a certain reserve. Fig. 105.—Section oe pakt of Stem 01? Bicinus communis. a, starch sheath; at the extremities of the figure its cells are represented as empty; &, cambium layer. shall be deposited not far from the growing cells, so that a slow continuous supply may be available. We find such reserves laid down near the cambium, either in the cells of definite sheaths surrounding the whole ring of new tissue (fig. 105, a), or in the spaces called medullary rays, which are found between the separate masses of wood and bast, these rays (fig. 106) being composed of cells which differ in shape from the typical forms of both wood and bast cells. In stems of smaller girth which have not developed much wood, we find stores of food laid up in the region 15. 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. Philadelphia, P. Blakiston
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