The ovary wall matures into the fruit wall known as the pericarp. It is made up of 3 layers. In some fruit all 3 layers develop but in others only one. Typically the middle layer (mesocarp) becomes fleshy, the outer layer (exocarp) may develop into the skin and the inner layer (endocarp) may become stony and surround the seeds. In other fleshy fruits such as in the Apple in the Rose Family, the hypanthium becomes part of the fruit as well as the ovary wall and these are also known as accessory fruits.
A berry is a stoneless fruit in which the ovary walls have produced a skin and a fleshy pulp that surround the seeds from a single ovary. Tomato, gooseberry, elderbery, grape, fuchsia and deadly nightshade are examples. In the tomato, the ovary has 2 locules and the photo above shows many ovules (seeds) in each locule growing on a swollen central (axile) placenta.
A hesperidium is a berry which has a thick rind and a very juicy interior divided into segments by septa. Typical of citrus fruits such as the orange, grapefruit and lemon. In the orange shown here there are ten segments (locules) formed from ten united carpels. The segments are filled with juice sacs and seeds and the septa are white.
A drupe consists of 3 of the ovary wall layers – an outer skin, a fleshy middle layer and an inner stony layer which surrounds the seed. Cherry, Blackthorn, Olive, Apricot, Peach and Plum fruits are drupes. They are often known as Stone fruits and are usually formed from a single-seeded ovary.
A pome consists of a core formed by the inner wall of several united carpels enclosed within a fleshy part made up from the outer walls and the hypanthium. Apple, Pear, Quince, Rowan, Hawthorn and Whitebeam fruits are pomes. This is an accessory fruit because it includes tissue from the hypanthium.