Leaf anatomy. Illustration of the distinctive structure of the leaves found in plants that obtain energy by C4 photosynthesis. This is known as the 'Kranz anatomy'. The vascular bundles consist of tubes of xylem (red) and phloem (green). These vascular bundles are surrounded by bundle sheath cells and mesophyll cells. These cells contain chloroplasts (green dots) that perform different functions in the photosynthesis process. Also shown are the upper epidermis (dark green, top), and the stoma (two at bottom), pores through which gas exchange takes place. For this artwork with labels, see image C023/8819.