Origin and Activity of Cork Cambium
The increases in diameter of stem due to secondary growth exerts a great pressure on outer tissue, rupturing the cortex and epidermis. As a result, the outermost layer of cortex becomes meristematic and begins to divide. This is known as cork cambium or phellogen. Its activity is more towards outside than inside. The cells formed on outerside constitute cork or periderm and those on inner side from secondary cortex or phelloderm. The latter consists of living parenchyma cells.
Bark. All dead tissue lying outside the cork cambium are known as bark i.e. reptured epidermis, hypodermis and cork.
Lenticels. At places, bark exhibits some aerating pores called lenticels for gaseous exchange. It is a slightly upraised oval performation in bark. In region of lenticel the cork cambium forms loose parenchymatous cells called complementary cells.
