It is the outermost layer and it covers the whole trunk region of the plant.
It has epidermal tissue.
A strip of secondary meristem replaces the epidermis of the stem.
To generate bark, cells on the outside edge of this layer are chopped off.
Several layers of thick bark are formed in a tree.
The periderm of secondary thickening organs, as well as the bark of woody stems and the roots of dicotyledonous flowering plants, include lenticels, which are porous tissues made up of cells with vast intercellular spaces.
Lenticels function as a pore, allowing direct gas exchange between internal tissues and the atmosphere via the bark, which would otherwise be gas-impervious. A small pore near the stomata of a plant allows gaseous exchange between the plant's internal and external environments.