During the development of the fruit, the wall of the ovary, called per carp, usually thickens and becomes differentiated into three layers, which may or may not be easy to distinguish visually. These layers are called the Exocarp, Mesocarp, and endocarp. As an example, in the peach, the Exocarp is the skin, the Mesocarp is the fleshy part, and the endocarp is the stony pit. The seed, containing the embryo, is inside the pit.

More special seed structural features:

• Hilum and funiculus: Funicular scar on seed coat that marks the point at which the seed was attached via the funiculus to the ovary tissue.
• Micropyle: The Micropyle is a canal or hole in the coverings (seed coat) of the nucellus through which the pollen tube usually passes during fertilization. Later, when the seed matures and starts to germinate, the micropyle serves as a minute pore through which water enters. The micropylar seed end has been demonstrated to be the major entry point for water during tobacco seed imbibition and germination. During germination the tobacco testa ruptures at the micropylar end and the radicle protrudes through the micropylar endosperm.
• Chalaza: Non-micropylar end of the seed. The base of an ovule, bearing an embryo sac surrounded by integuments.
• Raphe: Ridge on seed coat formed from adnate funiculus.
• Arillate: General term for an outgrowth from the funiculus, seed coat or chalaza; or a fleshy seed coat.
• Aril: Outgrowth of funiculus, raphe, or integuments; or fleshy integuments or seed coat, a sarcotesta. Arils probably often aid seed dispersal, by drawing attention to the seed after the fruit has dehisced, and by providing food as an attractant reward to the disperser. The aril of the nutmeg produces the spice mace and the seed itself is the nutmeg.
• Strophiole: Outgrowth of the hilum region which restricts water movement into and out of some seeds. In some hard-coated legume seeds, e.g. Melilotus alba and Trigonella arabica, a plug covering a special opening - the strophiolar cleft - must be loosened or removed before water can enter, and then only through this region.
• Operculum: A little seed lid. It refers to a dehiscent cap of a seed or a fruit that opens during germination.
• Carunculate: Seed with an excrescent outgrowth from integuments near the hilum, as in Euphorbia.
• Fibrous: Seed with stringy or cord-like seed coat, as mace in Myristica.
• Funicular: Seed with a persistent elongate funiculus attached to seed coat, as in Magnolia.
• Strophiolate: Seed with elongate aril or strophiole in the hilum region.
• Fruit: Strictly, the ripened ovary of a plant and its contents. More loosely, the term is extended to the ripened ovary and seeds together with any structure with they are combined, e. g. the apple (a pome) in which the fruit (core) is surrounded by flesh derived from the floral receptacle.
• Achene: A small, usually single-seeded, dry indehiscent fruit, e.g. lettuce.
• Caryopsis: A dry, nut-like fruit typical of grasses, e. g. a cereal grain. It is an achene with the ovary wall united with the seed coat.
• Elaiosomes: A specialty in the dispersal through animals is that through ants (myrmecochory). Such seeds or fruits bear attachments, the elaiosomes that contain lures and nutriments. Myrmecochory is common with plants that live at the forest soil like violets (Viola).

• Caruncle: A reduced aril, in the form of a fleshy, often waxy or oily, outgrowth near the hilum of some seeds. Usually it is brightly colored. It acts as an aid to dispersal. Viola seeds have an oily caruncle and are sought and dispersed by ants.
• Mucilage: A layer of polysaccharide slime produced by some seeds upon imbibition. Serves in water uptake during imbibition and germination.