. A class-book of botany, designed for colleges, academies, and other seminaries. Illustrated by a flora of northern, middle, and western states; particularly of the United States north of the Capitol, lat. 38 3/4. Botany; Plants; Plants. ALDURNUM AND DURAMEN. 79 number of layers, if counted at the base, will correctly indicate the age of the tree. 202. Each woody layer is composed of ligneous fibre, vasi- fprzQ tissue, arid ducts (33,/). The first gives strength and solid- ity to the trunk, and determines the direction of the cleavage. a. The duct* are always first formed and lie in the inner
. A class-book of botany, designed for colleges, academies, and other seminaries. Illustrated by a flora of northern, middle, and western states; particularly of the United States north of the Capitol, lat. 38 3/4. Botany; Plants; Plants. ALDURNUM AND DURAMEN. 79 number of layers, if counted at the base, will correctly indicate the age of the tree. 202. Each woody layer is composed of ligneous fibre, vasi- fprzQ tissue, arid ducts (33,/). The first gives strength and solid- ity to the trunk, and determines the direction of the cleavage. a. The duct* are always first formed and lie in the inner part next the centre, while the fibrn are produced towards the end of the season, and arc deposited in the outer parts of the zone. The former are distinguished by the large size of their open ends, while tin; woody fibres are more minute and compact. This cir- cumstance renders the limits of each layer distinctly perceptible in a cross section of the b c d c (1 c (I c RIO. 36.—Sections of wood ; i, :>, :, spiral vessels of the medullary sliealh, e, doUed ducts, d, woody fibre, e, hark ; :t, Endogen- ii, exhibiting the bundles of woody fibre, spiral vessels, and duets, Irregularly d in the cellular tissue ; 5, a, cellular tissue, b, spiral vessels on inner side of c, dotted ducts, d, woody fibre on the exterior side. 0, Laticifer of the bark. 20.'5. The outer and more recent portion of the layers constitutes the 4LBTJB- m m (a/frus, white), or sap-wood, Thia is usually of a softer structure and lighter color than the reel of the wood, and It is through the re seeklof thete layers alone, that the Sap aSCendfl. The inferior layers of the alhurniini gradually harden l»y the deposition Of solid secretions in their vessels, until they can no longer allow the pa isage of fluids through them. Thus the dub \mkn [durut, hard), or heart" wood Is formed, the texture of which is firm and durable. It i> only the dura- men which is useful in the Please note that
Size: 2031px × 1230px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade, booksubjectbotany, booksubjectplants
