Medullary ray (botany)

They appear as radial planar structures, perpendicular to the growth rings, which are visible to the naked eye.

[citation needed] These medullary or pith rays are essential for the radial conduction of the water, minerals and other organic substances.

[citation needed] In this context, the term refers to radial sheets or ribbons extending vertically through the tree across and perpendicular to the growth rings.

Also called pith rays or wood rays, these formations of primarily parenchyma cells allow the radial transport of sap and are essential in the process of tylosis.

[citation needed] In quartersawn material, where the wood is cut into boards with the growth rings roughly perpendicular to the face of the board, the medullary rays often produce beautiful figure such as silver grain, medullary spots, pith flecks, etc.