What are pores in the layer of bark called?

Lenticels are tiny pores that protrude from the cork and allow the gaseous exchange to occur.

Lenticels are common in old dicot stems, and their primary function is known to be gas exchange. 

Lenticels are one among the many pores in the stem of a woody plant which allow the exchange of gases between surroundings and internal tissues.

Stomata are small openings or pores found on the surface of leaves and stems that allow for the exchange of gases (such as carbon dioxide and oxygen) and water vapour between the plant and the environment.

The cuticle is a waxy layer that covers the surface of leaves and stems, helping to reduce water loss through transpiration by forming a barrier against water loss.

Guttation is the process by which plants excrete excess water in the form of droplets from specialized structures called hydathodes, usually found at the tips of leaves.