. The essentials of botany. Botany. 66 GEOUPS OF TISSUES, OR TISSUE SYSTEMS. Fig. 34.—Starch storage cells of potato. tions of the plant and of giving buoyancy to the part in which they occur. 97. Another important function of tissues is that of storage of food substances. Storage tissues are usually composed of large parenchyma cells with large central vacuoles and compara- tively little protoplasm. In some special cases where the storage product is one of the hemicelluloses this is deposited against the cell wall forming a sort of sclerenchyma tissue. 98. In many plants a"re found secre
. The essentials of botany. Botany. 66 GEOUPS OF TISSUES, OR TISSUE SYSTEMS. Fig. 34.—Starch storage cells of potato. tions of the plant and of giving buoyancy to the part in which they occur. 97. Another important function of tissues is that of storage of food substances. Storage tissues are usually composed of large parenchyma cells with large central vacuoles and compara- tively little protoplasm. In some special cases where the storage product is one of the hemicelluloses this is deposited against the cell wall forming a sort of sclerenchyma tissue. 98. In many plants a"re found secretory cells. These often line closed cavities (or "reservoirs") or elongated passages. These cavities or passages may be formed simply by the pushing apart of certain cells as the secretion is poured into the space between them ( produced schizogenously) or certain cells may be dissolved, forming "lysigenous" cavities. Good examples of the first type are shown by the gum canals of the ivy {Hedera helix) and the tur- pentine canals of conifers or the glands of the leaves of St. John's wort (Hypericum). In the leaves and fruits of Rutaceae the cavities more often arise by the dissolving of the secretory cells thus setting free the secretion within a cavity. The secretions are usually gums or ethereal oils, often containing resins, etc. Other cells containing crystals of calcium oxalate and other substances, perhaps including tannin, may possibly be classed as excretory organs in which the excretions are stored up in the absence of any structure that would permit their being thrown out of 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 Bessey, Charles E. (Charles Edwin), 1845-1915; Bessey, Ernst Athearn, 1877-1957. joint author. New York, H. Holt and company
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