. 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. mposed of concentric zones, or layers,pervaded and intersected by the medullary rays (204). Thefirst, or imier layer, together with the pith and medullary sheath,is the product of the first year. One new layer is formed eachsuccessive year, during the life of the plant; hence the whole ALBURNUM AND DURAMEN. 79 number of layers, if counted at the base, will correctly indicatet
. 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. mposed of concentric zones, or layers,pervaded and intersected by the medullary rays (204). Thefirst, or imier layer, together with the pith and medullary sheath,is the product of the first year. One new layer is formed eachsuccessive year, during the life of the plant; hence the whole ALBURNUM AND DURAMEN. 79 number of layers, if counted at the base, will correctly indicatethe age of the tree. 202. Each woody layer is composed of hgneoiis fibre, vasi-forni tissue, and ducts {So,/). The lirst gives strength and sohd-ity to the tiunk, and deteruiines the cUrection of the cleavage. a. The ducts arc always first formed and lie in the inner part next the centre,while the /Ibrcs arc produced towards the end of the season, and arc deposited inthe outer parts of the zone. The former are distinguished by the large size oftheir open ends, while the woody fibres are more minute and compact. This cir-cumstance renders the limits of each layer distinctly perceptible in a cross sectionof the b c (.1 c d c d e FIG. 26. — Sections of wood ; 1, 2, 3, horizontal, 4, 5, vertical. 1, Exogenous stem of oneyears growth; a, pith, 6, bark, c, medullar}- rays, rf, woody bundles of fibre and vessels;2, stem of three years growth, a, pith, e, bark, b, c, d, successive annual layers; 4, a, pith, b,spiral vessels of the medullary sheath, c, dotted ducts, d, woody fibre, e, bark ; 3, Endogen-ous stem, exhibiting the bundles of woody fibre, spiral vessels, and ducts, irregularly disposedin the cellular tissue ; 5, a, cellular tissue, b, spiral vessels on inner side of c, dotted ducts, d,woody fibre on the exterior side. 6, Laticiferous vessels of the bark. 203. The outer and more recent portion of the layers constitutes the albur-KUM {albus, wiiite), or sap-wood. This
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectbotany, bookyear1848
