Definition of medullary ray in English:

medullary ray

noun

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 (obsolete).

Origin

Early 19th century; earliest use found in Patrick Keith (1769–1840).