Give an explanation about cork cambium.

(N/A) $\Rightarrow$ As the stem continues to increase in girth due to the activity of the vascular cambium,the outer cortical and epidermal layers get broken and need to be replaced to provide new protective cell layers.
$\Rightarrow$ Hence,sooner or later,another meristematic tissue called cork cambium or phellogen develops in the cortex region.
$\Rightarrow$ It is a couple of layers thick and is made of narrow,thin-walled,and nearly rectangular cells.
$\Rightarrow$ The phellogen cuts off cells on both sides; the outer cells differentiate into cork (phellem) and the inner cells differentiate into secondary cortex (phelloderm).