Dutchman's pipe plant stem. Light micrograph of a section through the stem of a dutchman's pipe plant (Aristolochia sipho). The inner blue circle is a layer of sclerenchyma fibres, it is a strong tissue that forms a second wall for support of the plant. As the stem grows wider the sclerenchyma ring ruptures. To maintain the strength of the wall the parenchyma tissue in the gaps is transformed into bundles of sclerenchyma tissue, or sclereids. Within the sclerenchyma ring is a layer of phloem cells. The phloem transports carbohydrates and plant hormones around the plant. The bundles of cells, (purple) are xylem cells. The xylem transports water and mineral nutrients from the roots throughout the plant.