A plant tissue consisting of actively dividing cells (see meristem) that is responsible for increasing the girth of the plant, i.e. it causes secondary growth. The two most important cambia are the vascular (or fascicular) cambium and the cork cambium. The vascular cambium occurs in the stem and root; it divides to produce secondary xylem and secondary phloem (new food- and water-conducting tissues). In mature stems the vascular cambium is extended laterally to form a complete ring: the sections of this ring between the vascular bundles comprise the interfascicular cambium. Compare apical meristem.