The New Student's Reference Work/Cambium
Camb′ium (in plants), the layer of living cells between the wood and bark, which has the power of making additions to both. Such cells have the power of dividing and thus forming new cells, on the inside adding new wood cells, thus adding each year to the rings of wood, and on the outside new bark cells. Cells with this power of division are generally knows as meristematic cells, and cambium is merely a meristem which occurs between wood and bark. These delicate cells are exposed when bark is peeled from a tree, forming the glairy, mucilaginous substance which makes the line of easy cleavage.