. Beginners' botany. Botany. THE STEMâITS GENERAL STRUCTURE 65 fi an. £3 ^ ^ ^ ^ ^ Cs ^ g=sd Si '"T. larger, even if the tree should live a century. It is not quite inclosed, however, for the narrow layers of soft cells separating the bundles remain be- tween them (Fig. 78), forming ra- diating lines called medullary rays or pith rays. The Several Plant Cells and their Functions. â In the wood there are some parenchyma cells that are still with thin walls, but have lost the power of di- vision. They are xvovi storage cells. F'g. 78. âarrangement of Tissues in Two-year- 1 here are also ol
. Beginners' botany. Botany. THE STEMâITS GENERAL STRUCTURE 65 fi an. £3 ^ ^ ^ ^ ^ Cs ^ g=sd Si '"T. larger, even if the tree should live a century. It is not quite inclosed, however, for the narrow layers of soft cells separating the bundles remain be- tween them (Fig. 78), forming ra- diating lines called medullary rays or pith rays. The Several Plant Cells and their Functions. â In the wood there are some parenchyma cells that are still with thin walls, but have lost the power of di- vision. They are xvovi storage cells. F'g. 78. âarrangement of Tissues in Two-year- 1 here are also old stem of moonseed. wood fibers which AP'A; /.parenchyma. The fibro- , . , n J vascular bundles, or wood are iniCK-Waiieu strands, are very prominent, wUh and rigid ih Fig. *'" '"'^''""^'â y "y^ between. "jG), and serve to support the sap-canals or wood vessels (or tracheids) that are formed by the absorption of the end walls of upright rows of cells; the canals pass from the roots to the twigs and even to ribs of the leaves and serve to transport the root water. They are recognized (Fig. 79) by the peculiar thickening of the wall on the inner surface tubes, occur- ring in the form of spirals. Sometimes the whole wall is thickened except in spots called pits {g, Fig. y6). These thin spots (Fig. 80) allow the sap to pass to other cells or to neighboring vessels. The cambium, as we have seen, consists Longitudinal section of wall at o, showing of cells whose function is growth. These pit borders at o,». Fig. 79. â Markings IN Cell- W^alls OF Wood Fibers. sp, spiral; an^ annular ; sc, 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 Bailey, L. H. (Liberty Hyde), 1858-1954. New York, The Macmillan company
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Keywords: ., bookauthorbai, bookcentury1900, bookdecade1900, booksubjectbotany
