. A class-book of botany, designed for colleges, academies, and other seminaries ... Illustrated by a flora of the northern, middle, and western states; particularly of the United States north of the Capitol, lat. 38 3/4. being a long, slender tube, tapering each way, but is tliin-ner and weaker. Its pecuhar mark is an elastic, spiral fibre,coiled up within it, from end to end. b. The spiral thread is usually single, sometimes double, triple, &c. In theChinese pitcher plant, it is quadruple. (Fig. 1,/.) c. In size, spiral vessels are variable. Generally their diameter is aboutof an inch; often
. A class-book of botany, designed for colleges, academies, and other seminaries ... Illustrated by a flora of the northern, middle, and western states; particularly of the United States north of the Capitol, lat. 38 3/4. being a long, slender tube, tapering each way, but is tliin-ner and weaker. Its pecuhar mark is an elastic, spiral fibre,coiled up within it, from end to end. b. The spiral thread is usually single, sometimes double, triple, &c. In theChinese pitcher plant, it is quadruple. (Fig. 1,/.) c. In size, spiral vessels are variable. Generally their diameter is aboutof an inch; often not more than -g-ijinj- d. The situation of spiral vessels is in the medullary sheath, that is, just aroundthe pith; also in every part which originates from it, such as the veins of leaves,petals, and other modifications of leaves, and especially in the petioles, fromwhich it may be uncoiled, in the manner above described. (28, a.) e. In their perfect state they contain air, which they transmit, in some way,from one to another. f. Ducts are membranous tubes, with conical or rounded ex-tremities, their sides being marked with transverse bars, rings,or coils, incapable of being unrolled witliout breaking. 1000. FIG. 2. — Forms of tissue, &c.; a, annular ducts; b, spiral and annular at intervals; c,laticiferous tissue ; e, stomata of iris — vertical section, d, d, green cells at the orifice ; /, _/,cells of the parenchyma, e, air-chamber; g, g, view of epidermis and stomata of yucca, A,Btomata closed; small, luminous bodies in the cells. 3 24 ELEMENTARY ORGANS. g. In tliis modification of spiral vessels the tube is much lengthened, and thecoil within it is either dosed, that is, will not um-oll, as in the ferns; or it is anmi-lar, that is, broken into distinct rings, as in the garden balsam; or it is reticulated,that is, branching, the branches crossing so as to form a net-work. The office ofall these ducts is the same, — that of conveying fluid. It is only in the spiralve
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectbotany, bookyear1848
