mer·i·stem (měr'ĭ-stěm') n. The undifferentiated plant tissue from which new cells are formed, as that at the tip of a stem or root.
[Greek meristos, divided (from merizein, to divide, from meris, division; see (s)mer-2 in Indo-European roots) + -em (as in xylem and phloem).] mer'i·ste·mat'ic (-stə-māt'ĭk) adj., mer'i·ste·mat'i·cal·ly adv.