Tilia stem. Light micrograph (LM) of a young stem.Tilia is a genus of about 30 species of trees or bushes, native throughout most of the temperate Northern Hemisphere. Tilia have a dicot stem vascular arrangement. 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 (called pith and cortex) develops support cells to hold the young plant upright. The dicot stem has a distinct ring of vascular bundles. Magnification: x10 at 10 cms. wide.