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

Explanation

The commerical cork is obtained from the cork tissue of Quercus suber, which yields bottle cork. Cork is formed by cork cambium or phellogen cell. Cork cambium cells divide periclinally, cutting cells towards the inside and outside The cells cut off two wards the outside become suberised and dead.
These are compactly packed in radial rows without intercellular spaces and form cork of phellem. Cork is imprevious to water due to suberin and provides protection to the underlying tissues.