cross section: Zea stem magnification: 100x

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The vascular bundles in the roots and stems of monocots are typically closed, meaning the xylem and phloem are adjacent to each other. There is no vascular cambium, limiting the possibility of secondary growth. The vascular tissues are often wrapped in a bundle sheath of starch containing parenchyma or, in the case of Zea, supportive, heavy walled sclerenchyma.