How does the arrangement of vascular tissues help distinguish plant groups?

In the study of plant morphology, the arrangement of vascular tissues—specifically xylem and phloem—is a primary diagnostic feature used to distinguish between major groups of vascular plants.12

The most significant distinction is found between monocots and dicots:

• Monocots: Their vascular bundles are typically scattered throughout the stem's ground tissue. These bundles are often "closed," meaning they lack vascular cambium, which prevents the plant from increasing in girth through secondary growth.13
• Dicots: Their vascular tissues are organized into a ring that surrounds a central pith. In woody dicots, the presence of vascular cambium allows for the production of secondary xylem, which forms the annual growth rings characteristic of trees.134

Furthermore, the internal structure of the bundles themselves helps identify plant types. In dicots, bundles are often "collateral," with phloem positioned on the exterior side of the xylem. While all vascular plants share these conducting tissues, the complexity and specific cellular composition—such as the presence of specialized vessel members in angiosperms versus the simpler tracheids found in most gymnosperms—further differentiate these groups.154