Cambium

n.	1.	(Bot.) A series of formative cells lying outside of the wood proper and inside of the inner bark. The growth of new wood takes place in the cambium, which is very soft.
	2.	(Med.) A fancied nutritive juice, formerly supposed to originate in the blood, to repair losses of the system, and to promote its increase.

Noun	1.	cambium - formative one-cell-thick layer of tissue between xylem and phloem in most vascular plants that is responsible for secondary growth
	2.	cambium - the inner layer of the periosteum

vascular tissue