cambium

(pl.: cambia) A one or two cells thick layer of plant meristematic tissue, between the xylem and phloem tissues, which gives rise to secondary tissues, thus resulting in an increase in the diameter of the stem or root. The two most important cambia are the vascular (fascicular) cambium and the cork cambium.

The layer of reproducing cells between the inner bark (phloem) and the wood (xylem) of a tree that repeatedly subdivides to form new wood and bark cells.