Woody stem section. Coloured scanning electron micrograph (SEM) of a transverse section through the stem of a woody plant. The majority of tissue seen here is secondary xylem (dark brown), which transports water and mineral nutrients from the roots throughout the plant. Forming a thin ring around the xylem is the phloem (beige), which transports carbohydrates and plant hormones around the plant. The outer tissue of the stem (light brown) is the bark. Magnification: x30 when printed 10 centimetres wide.