Grass stem. Coloured scanning electron micrograph (SEM) of a section through a grass stem (family Graminaceae). The surface is covered in a waxy epidermis (green) that helps to prevent water loss. Within the stem are vascular bundles (red), which consist of phloem and xylem tissues. Xylem transports water and mineral nutrients from the roots throughout the plant, while the phloem transports carbohydrates and hormones around the plant. Surrounding the vascular bundles is the cortex (brown). This is made up of sclerenchyma, which is supportive tissue, and parenchyma tissue, where the primary plant functions take place.