what is a lenticel?

Lenticels are small, corky, raised areas on the surface of stems and branches of woody plants, including trees. They function as tiny pores that allow for gas exchange between the internal tissues of the plant and the external environment. 

These pores enable the exchange of gases like oxygen and carbon dioxide, as well as water vapor. Lenticels are particularly important for gas exchange in woody plants because the outer layer of bark is often impermeable to gases. 

In appearance, lenticels can vary depending on the plant species, but they often appear as small, oval-shaped, or elongated spots or lines on the bark. In some species, such as birch trees, lenticels may be more pronounced and contribute to the distinctive appearance of the bark.