Merriam-Webster Collegiate Dictionary - xylem

 noun  Etymology: German, from Greek xylon  Date: 1873 a complex tissue in the vascular system of higher plants that consists of vessels, tracheids, or both usually together with wood fibers and parenchyma cells, functions chiefly in conduction of water and dissolved minerals but also in support and food storage, and typically constitutes the woody element (as of a plant stem) — compare phloem