Pea plant xylem. Coloured scanning electron micrograph (SEM) of a longitudinal section through the stem of a pea plant (Pisum sativum). Within the stem are xylem vessels. A xylem vessel is made up of individual cells that are dead. The cross walls separating individual cells have broken down to form a continuous tube-like structure, which is capable of transporting water and minerals from the roots to the rest of the plant. These vessels have a unique secondary wall thickening, which can be, for example, spiral (seen here). Magnification: X920 at 10 centimetres across.