What is the commercial source of cork? How is it formed in the plant?

(N/A) $\Rightarrow$ Commercially,cork is obtained from the cork cambium (phellogen) of the plant,specifically from the species $Quercus$ $suber$. The cork used for bottle stoppers is derived from this tissue.
$\Rightarrow$ Cork is formed through the activity of the cork cambium. The cells of the cork cambium divide periclinally (parallel to the surface) to cut off cells both towards the inside and the outside.
$\Rightarrow$ The cells cut off towards the outside differentiate into cork or phellem. These cells become suberized (deposition of suberin) and die at maturity.
$\Rightarrow$ These cells are radially arranged in compact rows without intercellular spaces. The presence of suberin makes the cork impermeable to water and gases,providing protection to the underlying tissues.