Which type of stem predominantly has its vascular system located just under the bark?

The vascular system in dicot stems is primarily located just beneath the bark. This anatomical structure allows for efficient transport of water, nutrients, and photosynthetic products throughout the plant. In dicots, the vascular bundles are arranged in a ring formation, which is characteristic of their growth patterns and contributes to the formation of the cambium layer. This cambium layer is responsible for secondary growth, leading to an increase in the thickness of the stem over time.

In contrast, the vascular systems of monocots are scattered throughout the stem rather than organized in a ring, making it less conducive to the same type of secondary growth found in dicots. Herbaceous stems tend to exhibit characteristics of both monocots and dicots, but they are not defined by a specific vascular arrangement just beneath the bark. Annual, on the other hand, refers to the life cycle of a plant rather than its structural vascular arrangement. Therefore, the identification of dicots with their vascular system located under the bark is key in understanding their growth and development.