The American botanist and florist; including lessons in the structure, life, and growth of plants; together with a simple analytical flora, descriptive of the native and cultivated plants growing in the Atlantic division of the American union . ed bast-cells, and are strength-ened with secondary deposits until quite filled up. Hence thestrength and toughness of flax and hemp. The strong materialof Russian matting is from the liber of the Linden-tree, andthe lace of the South Seas, from the Lace-bark tree. Theliber of other trees is not remarkable for strength. 413. The cellular^ or green Ijarh
The American botanist and florist; including lessons in the structure, life, and growth of plants; together with a simple analytical flora, descriptive of the native and cultivated plants growing in the Atlantic division of the American union . ed bast-cells, and are strength-ened with secondary deposits until quite filled up. Hence thestrength and toughness of flax and hemp. The strong materialof Russian matting is from the liber of the Linden-tree, andthe lace of the South Seas, from the Lace-bark tree. Theliber of other trees is not remarkable for strength. 413. The cellular^ or green Ijarh^ succeeds to the liber. Itstissue resembles that of the leaf—being filled with sap and 511 chlorophyl. It grows laterally, to accommodate itself to theenlarging circumference of the tree, butdoes not increase in thickness after thefirst few years. 414. The cortical^ or brown bark. Itscolor is not always brown, being rarelywhite (Canoe Birch), or straw-color (Yel-low Birch), or greenish (Striped Maple),or grayish (Beech, Magnolia). Its sub-stance is always cellular tissue, but dif-fering widely in consistency in difierentspecies. Its new layers come from with-in, formed from the green bark, whileits older are sooner or later cast 511, Wood of Oak—section longi-tudinal, showing, a, medullary rays;fe, wood-cells; c, porous ducts. 415. The cortical layers sometimes accumulate to aconsiderable thickness (Maple, Hickory, Oak), but arefinally rent and furrowed by the expanding wood. Inthe Cork Oak (Quercus suber) they attain an excessive growth, furnishing that usefulsubstance, corh. In Birch (Betula papj-racca) these layers resemble paper, long abidingby their elasticity tlie expansion of the trunk. 416. The medullary rays {medulla, pith) are those fine 136 PHYSIOLOGICAL BOTANY. lines which appear in a cross-section, passing like radii from thepith to the bark, intersecting the wood and dividing it int(wedge-shaped bundles or sectors. They consist of firm platesof parenchy
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectbotany, bookyear1870
