The part of a fruit that develops from the ovary wall of a flower. The type of fruit that develops depends on whether the pericarp becomes dry and hard or soft and fleshy. The pericarp can be made up of three layers. The outer skin (epicarp or exocarp) may be tough and hard; the middle layer (mesocarp) may be succulent as in peach, hard as in almond, or fibrous as in coconut; and the inner layer (endocarp) may be hard and stony as in many drupes, membranous as in citrus fruits, or indistinguishable from the mesocarp, as in many berries.