. The teacher's handbook of slöjd : as practised and taught at Naäs, containing explanations and details of each exercise. unt of thegrowth of trees; of the most important properties of wood,and the principal changes which it undergoes; and by acomparison of the technical qualities of the various kinds ofwood in common use. A. The Structure and Composition of Wood. Wood or timber forms the greater part of the stems andbranches of trees and shrubs. To examine the inner structure of a tree-stem, a section ^ tree-stemmay be made at right angles to the direction of its length, * section,, a tr
. The teacher's handbook of slöjd : as practised and taught at Naäs, containing explanations and details of each exercise. unt of thegrowth of trees; of the most important properties of wood,and the principal changes which it undergoes; and by acomparison of the technical qualities of the various kinds ofwood in common use. A. The Structure and Composition of Wood. Wood or timber forms the greater part of the stems andbranches of trees and shrubs. To examine the inner structure of a tree-stem, a section ^ tree-stemmay be made at right angles to the direction of its length, * section,, a transverse or cross section; or from the pith to thebark in the line of one of the radii and parallel to the direc-tion of the length, , a radial section; or a third sectionmay be made at right angles to both the preceding as atangent to the circumference, , a tangential section. 28: HANDBOOK OF SLOJD. On examiningthe cross-sectionof a stem we findan outer ring, the6ar^, consisting ofa corky layer, theouter bark, andthe inner bark orhast\ next comesthe wood, consti-tuting the chiefportion of thestem, and in the. Fig. 1. Three sections of a tree-stem, at rightangles to one another. T-wo->/>-<- id ^ T. cross section, A, radial section, r^. tangential section. cen^rai pari) is a _jf. medulla - ------ canal fillpd -wrifli annual layers, mm. Medullary rays, a&. thickness of medullary or pith, B. Bark, C. Cambium, aa. Concentrics, mm. Medullary rays, ab. thickn<rays, cd. height of medullary rays, II. vessels. soft cellular tissue called the pith or medulla. Between thewood and the bast lies a narrow, light-coloured ring, theCamhiuon. This consists of a layer of embryonic cells, fromwhich are developed on the one side wood, and on the otherbast, and it is here that the growth of the tree takes place. The Cambium forms the soft, moist, spongy mass whichmay be seen under the bark in spring when the sap beginsto rise. It consists of microscopic cells, some
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectmanualt, bookyear1892
