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

$\Rightarrow$ Commercially cork is obtained from cork cambium of plant. The cork of bottle is made from it. Cork is made from cells of cork cambium. The cells of cork cambium cut the cells from inside and outside periclinally. The cells which are cut outside become suberised and die.

$\Rightarrow$ They are radially arranged in rows without intercellular spaces and arranged properly. That creates phellem. Phloem is impermeable for water due to suberin and protects following tissues.