. Elements of botany. Plants. STRUCTURE OF THE STEM. 59 The pith forms a large part of the bulk of very young shoots, since it is a part of the fundamental tissue amid which the fibro-vascular bundles arise. In mature stems it becomes rather unimportant, though it often continues for a long time to act as a storehouse of nourishment. The medullary rays, in the young shoot, serve as a channel for the transference of water and plant-food in a liquid form across the stem, and they often contain much stored nourishment. The vessels carry water and air through the Fig. 49. — Longitudinal Sec
. Elements of botany. Plants. STRUCTURE OF THE STEM. 59 The pith forms a large part of the bulk of very young shoots, since it is a part of the fundamental tissue amid which the fibro-vascular bundles arise. In mature stems it becomes rather unimportant, though it often continues for a long time to act as a storehouse of nourishment. The medullary rays, in the young shoot, serve as a channel for the transference of water and plant-food in a liquid form across the stem, and they often contain much stored nourishment. The vessels carry water and air through the Fig. 49. — Longitudinal Section of a Fibro-Vascular Bundle of the Castor-Oil Plant. *'f gs, b,p, various layers of the bark; c, cambium; t I, s, s', various kinds of vessels; k, h', h", h' , wood-cells ; 7n, pith. (Much magnified.) The wood-cells of the heartwood are useful only to give stiffness to the stem. Those of the sapwood in addition to this work have to carry most of the water from the roots to the leaves and other distant portions of the plant. The cambium layer is the region in which the annual growth of the tree takes place, § 84. The most important portion of the inner bark is that which consists of sieve-tubes, for in these digested and elaborated plant-food is carried from the leaves toward 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 Bergen, Joseph Y. (Joseph Young), 1851-1917; Bergen, Joseph Y. (Joseph Young), 1851-1917. Bergen's Botany: key and flora, Pacific coast ed. Boston : Ginn
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectplants, bookyear1896
