| 单词 | medullary ray |
| 释义 | > as lemmasmedullary ray medullary ray n. [compare French rayon médullaire (1812)] Botany each of the sheets of tissue in the stem of a dicotyledonous plant that extend radially from the pith to the cortex between the vascular bundles (also called primary ray); (formerly also) †a secondary ray, in the secondary vascular tissue of a plant (see ray n.5 9a) (obsolete). ΘΚΠ the world > plants > part of plant > cell or aggregate tissue > [noun] > tissue > pith or soft internal tissue > medullary ray(s) insertment1671 ray1675 medullary ray1816 pith rayc1868 1816 P. Keith Syst. Physiol. Bot. I. 333 The divergent layers were at one time, and with some botanists are still, denominated Medullary Rays, upon the supposition of their originating in the pith. 1907 D. P. Penhallow Man. N. Amer. Gymnosperms vi. 88 In the higher Coniferæ the medullary ray is distinguished by the presence of an element which differs materially in its structure from the associated parenchyma cells. 1971 F. C. Ford-Robertson Terminol. Forest Sci. 213/1 The term medullary ray..is now restricted to the parenchyma connecting the primary cortex with the pith. < as lemmas |
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