Identifier: plantanatomyfrom00stev (find matches)
Title: Plant anatomy from the standpoint of the development and functions of the tissues, and handbook of micro-technic
Year: 1910 (1910s)
Authors: Stevens, William Chase, 1861-
Subjects: Botany -- Anatomy
Publisher: Philadelphia, P. Blakiston
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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rmis from e to a sheath or endodermis. The outer of thesezones, which includes the starch sheath, isknown as the primary cortex (Fig. 14).(The term primary cortex must not be confused with cortex as used in pharmacognosy, where cortex,employed synonymously with bark, is often applied to all ofthe tissues collectively which lie exterior to the cambium ring.)The primary cortex does not as a rule consist of a single tissue,but of two or more, so that in describing its evolution fromthe ground meristem the possible tissues composing it must beconsidered separately. Beginning at its exterior just beneath the epidermis we com-monly find a tissue whose walls are thickened at the angles wherethree or four cells join. This tissue is called the collenchyma(Fig. 14). It is one of the first of the primary tissues to cometo maturity, and its chief function, in virtue of its thickened inclusive; c, cystolith; b,palisade parenchyma; d,spongy parenchyma.<After Sachs.) THE PRIMARY PERMANENT TISSUES
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Pith Cambium FIG. 14.—Diagram to show the topography and character of the tissues that are evolvedfrom the primary meristems. Cambial activity has not yet begun. 32 DIFFERENTIATION OF THE TISSUES walls, is to give strength at a time when the bast and woodfibers have not yet made their appearance or arrived at suffi-cient maturity to be effective. It may occur as a continuouszone or in separate strands. In producing the collenchyma theground meristem cells divide transversely and vertically, thedaughter cells enlarge and elongate vertically; the walls graduallythicken at the angles, but the cellulose composing them does notappear to become essentially altered or replaced. The collen-chyma cells usually contain chloroplasts, and they remain livinguntil cut off from the general circulation by cork cells in theformation of borke (see page 55), as frequently happens inwoody plants. Thin-walled Parenchyma lies next to the collenchyma internally,and as a rule constitutes most of the primar

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