. Elements of plant anatomy;. Botany -- Anatomy. 130 ELEMENTS OF PLANT ANATOMY. The secondary parenchymatic and living element of the wood is the medullary ray cell which also forms a part of the phloem elements. The origin of the primary ray has been given and its function referred to. It is the only one extend- ing from pith to rind and so connecting these portions. As each successive year adds a new zone of growth, the distance between these rays is constantly widening toward the circum- ference, and a new supply of living cells is added by the forma- tion of new medullary rays. The cambium
. Elements of plant anatomy;. Botany -- Anatomy. 130 ELEMENTS OF PLANT ANATOMY. The secondary parenchymatic and living element of the wood is the medullary ray cell which also forms a part of the phloem elements. The origin of the primary ray has been given and its function referred to. It is the only one extend- ing from pith to rind and so connecting these portions. As each successive year adds a new zone of growth, the distance between these rays is constantly widening toward the circum- ference, and a new supply of living cells is added by the forma- tion of new medullary rays. The cambium cells which are about to produce these divide by walls at right angles to their long axes, thus forming a parenchymatic meristem. The rays so formed are named secondary^ or rays of the same order as the year in which they arise. Regarding the character of the separate cells, their shape is similar to that of the wood parenchyma; their position, however, is reversed, so that the long axis is at right angles with that of the stem. Their walls are rather thick, unlignified, and richly supplied with simple pores. As a rule the primary rays have a greater width in the cross-section than the secondary; that is, they are often two, three, and even more cells wide, while the secondary are often only a single cell in width. The depth of the ray varies Avith the habit of the plant. Some are the depth of only a single cambium cell, others of several. A cross-section of a stem of several years' growth presents the appearance of a circle composed of narrow, wedge-shaped. Diagrammatic cross-section through a three years' dicotyledonous stem (Type Ber- beris). x xylem. p pliloem. c cambium. i interfasicular cambium, vi pith, m' pith crown. M primary medullary rays. s secondary medullary rays of the first; s' of the second order. — (Wiesner.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearanc
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectbotanya, bookyear1895
