The Collaborative International Dictionary
Medullary \Med"ul*la*ry\, a. [L. medullaris, fr. medulla marrow: cf. F. m['e]dullaire.]
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(Anat.)
Pertaining to, consisting of, or resembling, marrow or medulla.
Pertaining to the medula oblongata.
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(Bot.) Filled with spongy pith; pithy.
Medullary groove (Anat.), a groove, in the epiblast of the vertebrate blastoderm, the edges of which unite, making a tube (the medullary canal) from which the brain and spinal cord are developed.
Medullary rays (Bot.), the rays of cellular tissue seen in a transverse section of exogenous wood, which pass from the pith to the bark.
Medullary sheath (Anat.), the layer of white semifluid substance (myelin), between the primitive sheath and axis cylinder of a medullated nerve fiber.
Usage examples of "medullary rays".
Both rhizome and root in transverse section exhibit a distinctly radiate appearance, the thin cortex or bark enclosing a large, pale, yellowish-white wood, which consists of narrow bundles with small pores, alternating with straight, whitish, medullary rays about six or eight cells in thickness.
The clean transverse section shows numerous medullary rays and altemate bands of bast parenchyma, thus giving it a chequered appearance.
Externally they are of a rusty brown and internally whitish, with fine, straight, medullary rays and a rather thick bark.