Clematis stem. Coloured scanning electron micrograph (SEM) of a section through a Clematis sp. stem. Within the central pith (green) are six vascular bundles (blue and orange). Each vascular bundle consists of xylem (blue) and phloem (orange) tissue. Xylem transports water and mineral nutrients from the roots throughout the plant and phloem transports carbohydrates and plant hormones around the plant. Around the pith is the cortex (brown), which consists of parenchyma cells. On the outside of the stem is the epidermis (yellow).