Buttercup stem. Coloured light micrograph of a section through a buttercup stem (Ranunculus sp.) showing the circular-shaped vascular bundle (right). The large white circles in this bundle are the cells of the xylem (green), which transports water and mineral nutrients from the roots throughout the plant. The smaller circles within this bundle are cells of the phloem, which transports carbohydrates and plant hormones around the plant. The xylem and phloem are surrounded by very large parenchyma cells, which support the stem. Magnification: x30 when printed at 10cm wide.