Vascular cambium

Vascular cambium is a part of the plant's meristem - the series of tissues consisting of embryonic (incompletely differentiated) cells from which the plant grows. It is the innermost layer of the plant's bark, between the xylem and phloem tissues. The vascular cambium grows both to the inside and to the outside. New cells deposited on the inside make up the secondary xylem; new cells to the outside make up the secondary phloem. (The word secondary differentiates these new tissues from the primary xylem and phloem, which derive from the apical meristem.)

See also: Cork cambium