The elements of botany for The elements of botany for beginners and for schools elementsbotany00gray Year: 1887 140 VEGETABLE LIFE AXD WORK. [SECTION IG, layer of â wood outside the preceding one, between that and the barii. This is exogenous growth, or outside-growing, as the name denotes. 430. Some new i)ark is formed every year, as well as new wood, the former inside, as the latter is outside of that of the year preceding. The ring or zone of tender forming . tissue between the hark and the wood has been called the Cambium Layer. Cambium is an old name of the physiologists for nutritive ju
The elements of botany for The elements of botany for beginners and for schools elementsbotany00gray Year: 1887 140 VEGETABLE LIFE AXD WORK. [SECTION IG, layer of â wood outside the preceding one, between that and the barii. This is exogenous growth, or outside-growing, as the name denotes. 430. Some new i)ark is formed every year, as well as new wood, the former inside, as the latter is outside of that of the year preceding. The ring or zone of tender forming . tissue between the hark and the wood has been called the Cambium Layer. Cambium is an old name of the physiologists for nutritive juice. And this thin layer is so gorged with rich nutritive sap when spring growth is re- newed, that the bark then seems to be loose from the wood and a layer of viscid sap (or cambium) to be poured out between the two. But there is all the while a connection of the bark and the wood by delicate cc\h, rapidly mul- tiplying and growing. 431. The Bark of a year-old stem consists of beginning next the wood, â This contains some 480 three parts, more or less distinct, namely, 1. The Liber or Fibrous Bark, the Luier Bark. wood-cells, or their equivalent, commonly in the form of bast or bast-cells (111, Fig. 44'4), such as those of Basswood or Linden, and among herbs those of flax and hemp, which are spun and woven or made into cordage. It also contains cells which are named sieve-ceWsi, on account of numerous slits and pores in their walls, by which the protoplasm of contiguous cells communicates. In woody stems, whenever a new layer of wood is formed, some new liber or inner bark is also formed outside of it. Fig. 473. Piucu of a .stem of Soft Maple, of a year old, cut crosswise and length- wise. Fig. 479. A portion of the same, magnified. Fig. 4S0. A snnll piece of the same, taken froni one side, reaching from tlie bark to the pith, and highly magnified: a, ;mall hit of the jiith; b, .spiral ducts of what is called the mrdiillary shrrith ; c, the wood; d, d, dotted ducts
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