Explain the structure and function of the cork cambium (phellogen).

(N/A) 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. Hence,sooner or later,another meristematic tissue develops in the cortex region,called the cork cambium or $Phellogen$.
$Phellogen$ is a couple of layers thick. It is made of narrow,thin-walled,and nearly rectangular cells. The $Phellogen$ cuts off cells on both sides.
The cells cut off on the outer side differentiate into cork or $Phellem$,while the cells cut off on the inner side differentiate into secondary cortex or $Phelloderm$.
The cells of $Phellem$ are impervious to water due to the deposition of suberin in their cell walls.
The cells of the secondary cortex are parenchymatous.
$Phellogen$,$Phellem$,and $Phelloderm$ are collectively known as the $Periderm$.
Due to the activity of the cork cambium,pressure builds up on the remaining layers peripheral to the $Phellogen$,and these layers eventually die and slough off.