Commercial source of cork is cork oak or Quercus suben
Cork is formed on the outerside by phellogen or cork
cambium. Phellogen is purely a secondary meristem
which generally develops from an outer layer of cortex
by dedifferentiation of cortical cells. The intercellular
spaces disappear. Phellogen cells start dividing on their
outer and inner sides. Cells formed on the outerside
remain compactly arranged. They undergo suberisation,
get filled with tannins and die. The tissue of dead, tannin
and air-filled suberised cells formed on outer side Of
phellogen is called phellen or cork. At some places
aerating structures called lenticels are also formed.