. The elements of botany for beginners and for schools. Plants. 140 VEGETABLE LIFE AND WORK. [SECTION 16. 478 layer of wood outside the preceding one, between that and the bark. This is exogenous growth, or outside-growing, as the name denotes. 430. Some new bark 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 bark 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 nut
. The elements of botany for beginners and for schools. Plants. 140 VEGETABLE LIFE AND WORK. [SECTION 16. 478 layer of wood outside the preceding one, between that and the bark. This is exogenous growth, or outside-growing, as the name denotes. 430. Some new bark 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 bark 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 cells, rapidly mul- tiplying and growing. 431. The Bark of a year-old stem consists of three parts, more or less distinct, namely, — beginning next the wood, — 1. The Liber or Fibrous Bark, the Inner Bark. This contains some wood-cells, or their equivalent, commonly in the form of bast or bast-cells (411, Fig. 444), such as those of Basswood or Linden, and among herbs those of flax and hemp, which arc spun and woven or made into cordage. It also contains cells which are named sieve-cdls, 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 480 Fig. 478. wise. Fig. 479. Fig. 4S0 Piece of a stem of Soft Maple, of a year old, cut crosswise and length- A portion of the same, magnified. A small piece of the same, taken from one side, reaching from the bark to the pith, and highly magnified: a, a small hit of the pith; b, spiral ducts of what is called the medullary sheath ; c, the wood; d, d, dotted ducts in the wood; e, e, annular ducts;/, the liber or inner bark;
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectplants, bookyear1887
