English: Cross section of the stem of a herbaceous dicot (garlic mustard Alliaria petiolata), showing the vascular bundles at left (with purple xylem cells and dusky grey phloem cells) that fringe the cortex, and (parenchyma, or thin-walled) pith cells to the right (turquoise blue), which are available as storage tissue for water, carbohydrates and other nutrients, which will sustain future growth. The cell walls consist to a great part of cellulose, a structural carbohydrate which is not used for energy, but supplies remarkable structural strength and prevents desiccation.