Lily stem. Light micrograph(LM) of a section through a part of a lily (Lilium) stem. A thin outer epidermis surrounds a layer of cortex. At the centre is the pith, which contains numerous vascular bundles (yellow). Vascular tissues transport water and dissolved substances inside the plant and helps support the stem. The two types of vascular tissue are xylem and phloem. Xylem carries water and dissolved ions from the roots to stems and leaves. Phloem carries dissolved sugars from the leaves to all other parts of the plant. Xylem has two kinds of conducting cells, tracheids and vessel elements. Ground tissue of the stem (pith and cortex) develops support cells to hold the young plant upright. The monocot stem has a random arrangement of vascular bundles with more of the bundles located toward the stem periphery than in the center Magnification: x80 when printed at 10 centimetres wide.