. The elements of botany for beginners and for schools. Botany. SECTION 16.] ANATOMICAL STRUCTURE. 133 these, or the prolongation of others, into hollow libres or tubes of various size. Two sorts of sucli transformed cells go together, and essentially form the 408. Wood. This is found in all common herbs, as well as in shrubs and trees, but the former have much less of it in proportion to the softer cellular tissue. It is formed very early in the growth of the root, stem, and leaves, — traces of it appearing in large embryos even while yet in the seed. Those cells that leugtiien, and at the sa
. The elements of botany for beginners and for schools. Botany. SECTION 16.] ANATOMICAL STRUCTURE. 133 these, or the prolongation of others, into hollow libres or tubes of various size. Two sorts of sucli transformed cells go together, and essentially form the 408. Wood. This is found in all common herbs, as well as in shrubs and trees, but the former have much less of it in proportion to the softer cellular tissue. It is formed very early in the growth of the root, stem, and leaves, — traces of it appearing in large embryos even while yet in the seed. Those cells that leugtiien, and at the same time thicken their walls form the proper Woody Fibre or Wood-cells ; those of larger size and, thinner walls, which are thickened only in certain parts so as to have peculiar markings, and which often arc seen 444 445 447 to be made up of a row of cylindrical cells, with the partitions between absorbed or bro- ken away, are called Ducts, or sometimes Vessels. There are all gradations between wood-cells and ducts, and between both these and common cells. But in most plants the three kinds are fairly distinct. 409. The proper cellular tissue, or ^tf/•<?«- chyma, is the ground-work of root, stem, and leaves; this is traversed, chiefly lengthwise, by the strengthening and conducting tissue, wood-cells and duct-cells, in the form of bundles or threads, which, in the stems and stalks of herbs are fewer and comparatively scattered, but in sluubs and trees so numer- rous and crowded that in the stems and all permanent parts they make a solid mass of wood. They extend into and ramify in the leaves, spreading out in a horizontal plane, as the framework of ribs and veins, which supports the softer cellular portion or parenchyma. 410. Wood-Cells, or Woody Fibres, consist of tubes, commonly between one and two thousandths, but in Pine-wood sometimes two or three hundredths, of an inch in diameter. Those from the tough bark of the Basswood,. Fio. 444. Magnified wood-cells of the b
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