pericarp

Wall of a fruit. It encloses the seeds and is derived from the ovary wall. In fruits such as the acorn, the pericarp becomes dry and hard, forming a shell around the seed. In fleshy fruits the pericarp is typically made up of three distinct layers. The epicarp, or exocarp, forms the tough outer skin of the fruit, while the mesocarp is often fleshy and forms the middle layers. The innermost layer or endocarp, which surrounds the seeds, may be membranous or thick and hard, as in the drupe (stone) of cherries, plums, and apricots.