• When the cells of medullary rays differentiated, they give rise to the new cambium called interfascicular cambium. • Loose parenchyma cells rupturing the epidermis and forming a lens-shaped opening in bark are called complementary cells. • Large colourless empty cells in the epidermis of grass leaves are called bulliform cells. • In dicot leave, vascular bundles are surrounded by large thick walled cells called bundle sheath cells.