The fruit and the seed

A fruit is the ripened ovary after fertilisation. If a fruit forms without fertilisation, it is parthenocarpic (and usually seedless, like some bananas). A fruit has a wall, the pericarp, around the seeds. In a fleshy fruit the pericarp has three layers: the outer epicarp, the middle mesocarp, and the inner endocarp.

Mango and coconut are drupes: they grow from a single-carpel, superior ovary and have one seed. In mango, the epicarp is the thin skin, the mesocarp is the sweet flesh you eat, and the endocarp is the hard stone. In coconut, the mesocarp is the fibrous husk.

A seed is made of a seed coat and an embryo. The embryo has a radicle (baby root), an embryonal axis, a plumule (baby shoot) and one or two cotyledons (seed leaves).

A dicot seed, like a soaked bean or gram: the seed coat has two layers, the outer testa and inner tegmen. The hilum is the scar where the seed was attached to the fruit; just above it is a tiny pore, the micropyle. Inside are two cotyledons, often fat with stored food, and the plumule and radicle. In some seeds, like castor, food is stored in a separate tissue, the endosperm (endospermic seeds). In bean, gram and pea, the endosperm is used up, so they are non-endospermous.

A monocot seed, like maize: the seed coat is fused with the fruit wall. A large endosperm stores food; its outer layer is the protein-rich aleurone layer. There is one shield-shaped cotyledon, the scutellum. The plumule is covered by a sheath, the coleoptile, and the radicle by another, the coleorhiza. Most monocot seeds are endospermic, but orchid seeds are not.