. Class-book of botany : being outlines of the structure, physiology and classification of plants : with a flora of the United States and Canada . Botany; Botany; Botany. 595, Cross-sections of an exogenous stem (Elm), of 2 yenrs' growth ; 1, pith, 2, 3, annual layers of wood, next the cambium, 4, baric; 596, and endogenous stem (Sorghum or Millet), where there is no distinction of layers. G99. The dtjeamen is of no account in vegetation, and is in this respect dead. Hence it often decays, leaving the trunlc hollow, and the tree at the same time as flourishing as ever. 700. The bark succeeds a
. Class-book of botany : being outlines of the structure, physiology and classification of plants : with a flora of the United States and Canada . Botany; Botany; Botany. 595, Cross-sections of an exogenous stem (Elm), of 2 yenrs' growth ; 1, pith, 2, 3, annual layers of wood, next the cambium, 4, baric; 596, and endogenous stem (Sorghum or Millet), where there is no distinction of layers. G99. The dtjeamen is of no account in vegetation, and is in this respect dead. Hence it often decays, leaving the trunlc hollow, and the tree at the same time as flourishing as ever. 700. The bark succeeds and replaces the epidermis, covering and protecting the wood. It is readily distinguished into three parts, viz.: The inner, white bark (liber), The middle, green bark (cellular), The outer, brown bark (cortical). The substance of all these is parenchyma and arranged, like the wood, in layers. 701. The liber or white bark contains scattered bundles of pleuren- chyma and cienchyma with its cellular tissue. Its wood-cells are very long (§ 666), called bast-cells, and are strengthened with secondary de- posits until quite filled up. Hence the strength and toughness of flax and hemp. The strong material of " Eussian matting" is from the liber of the linden-tree, and the " lace" of the South Seas from the lace-bark tree. The liber of other trees is not remarkable for strength. 702. The cellular ok green bark succeeds to the liber. Its tissue resembles that of the leaf, being filled with sap and chlorophylle. It grows laterally to accommodate itself to the enlarging circumference of the tree, but does not increase in thickness after the first few years. 703. The cortical or brown bark. Its color is not always brown, being rarely white (canoe birch), or straw-color (yellow birch), or green- ish (striped maple), or grayish (beech, magnolia). Its substance is al- ways cellular tissue, but differing widely in consistency in dififerent species. Its new layers come from
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