Typical Monocot Vascular Bundles have extremely large Xylem (X) Vessel Members. Their Phloem is highly organized & contains large and small cells. The Sieve Tube Members (S) have the largest diameter. The small cells are Companion Cells (CC). These regulate phloem transport. Sclerenchyma Fibers form an external Bundle Sheath. This provides most of the structural support for these bundles.

Typical Dicot Vascular Bundles: The Xylem & Fibers are easy to identify because they both have thick, Lignified cell walls which stain red in most cases. The Fibers and the Xylem provide most of the structural support and the Fibers provide most of this. Phloem cells generally have thin, unlignified cell walls & are almost always found adjacent to the Xylem.