The vascular cambium normally gives rise to

Vascular cambium located between xylem and phloem in the stems and roots of vascular plants. It produces secondary xylem towards the pith and secondary phloem towards the bark.
Phellogen is made of narrow thin - walled and nearly rectangular cells . phellogen cuts off cells on both sides . the outer cells differentiate into cork or phellem while inner cells differentiate into secondary cortex or phelloderm. the phellogen, phellem and phelloderm are collectively known as perderm.