. Outlines of botany for the high school laboratory and classroom (based on Gray's Lessons in botany) Prepared at the request of the Botanical Dept. of Harvard University. Botany; Botany. MlNUTK A^ATUMY OF FLOWELiING PLANTS 223 bundle is surv ninded by a slieath of thick-walled lignified tissue, to which it largely owes its tensile strength. Once formed from the general formative tissue of the stem, the bundle shows no further growth, no annual increase of xylem and phloem. STRUCTURE OF STEMS 516. On one or the other of two types the stems of phanerogamous plants are constructed. In one, the w
. Outlines of botany for the high school laboratory and classroom (based on Gray's Lessons in botany) Prepared at the request of the Botanical Dept. of Harvard University. Botany; Botany. MlNUTK A^ATUMY OF FLOWELiING PLANTS 223 bundle is surv ninded by a slieath of thick-walled lignified tissue, to which it largely owes its tensile strength. Once formed from the general formative tissue of the stem, the bundle shows no further growth, no annual increase of xylem and phloem. STRUCTURE OF STEMS 516. On one or the other of two types the stems of phanerogamous plants are constructed. In one, the wood is made up of separate bundles, scattered here and there throughout the whole diameter of the stem. In the other, the wood is all collected to form a layer between a central cellular part ^vhich has none in it, the jnth, and an outer cellular pai't, the harJc. 517. An Asparagus shoot and a Cornstalk for hei'bs, and a Rattan for a woody kind, represent the first. To it belong all monocotyledons. A Beanstalk and the stem of any common shrub or tree represent the second; and to it belong all plants with dicotyledon- ous or })olycotyledonous embryo. The first has Iwen called, not very properly, endoffetious, which means inside grow- ing ; the second, properly enough, exo- ffeiioi(s, or outside growing. 518. Endogenous stems, those of mono- cotyledons, attain their greatest size and most characteristic development in P-alms and Dragon trees. A typical endoge- nous stem has no clear distinction of pith, bark, and wood, concentrically arranged, no silver grain, no annual layers, no bark that peels off clean from the wood. 519. Exogenous stems, those of plants coming from dicotyledonous and also polycotyledonous embryos, have a structure which is familiar in the wood of our ordinary trees and shrubs. It is the same in an herba-. 375. structure of a Cornstalk, in transverse and longitu- diual section. The dots on the cross sec- tion repre- sent cut ends of the woody Please
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