Vascular bundles in monocotyledons are considered closed because: There are no vessels with perforations; Xylem is surrounded all around phloem; Cambium is absent; A bundle sheath surrounds each bundle.

In a monocotyledenous stem, the vascular bundles are not arranged in a circle but are usually scattered throughout the ground tissue. There is no clearly defined pith as there is in many dicotyledonous species. As in the dicots, the xylem of the bundles is pre-orientated toward the middles of the stem.The vascular bundles of monocotylenous plants do not contain a layer of meristematic tissue (cambium) as the dicots do. Thus, no new cells can be formed inside the vascular bundles of monocots and their vascular bundles are termed closed whereas those of dicot plants are open.