Vascular cambium.
<P>
<lI> Types of cell division.
A cambium cell can divide transversely to form more cambium cells.
Radial division produces xylem (X) or phloem (P) cells.
<lI> Secondary growth.
Repeated radial divisions build up layers of xylem and phloem.
The cambium usually produces much more xylem (wood) than phloem.