the woody vascular tissue of a plant, characterized by the presence of vessels or tracheids or both, fibers, and parenchyma, that conducts water and mineral salts in the stems, roots, and leaves and gives support to the softer tissues
See xylem in American Heritage Dictionary 4
(zīˈləm)
noun
The supporting and water-conducting tissue of vascular plants, consisting primarily of tracheids and vessels; woody tissue.