All flowers become fruits. If you are unsure whether something is a fruit or not, check for seeds. Vegetables originally got their name for being derived from the vegetative (non-reproductive) part of the plant, such as a stem, root, or leaf.
The ovary wall surrounds the developing seeds and becomes the pericarp (peri- meaning around, carp- meaning fruit or body). The pericarp is composed of three layers:
- Exocarp - the outermost layer, making up the exterior surface of the fruit
- Mesocarp - the tissue located between the exocarp and endocarp
- Endocarp - the innermost layer, located just outside the seed coat
In some fruits these layers are distinctly different and easy to distinguish. In other fruits, the layers are fused together and nearly impossible to differentiate. Fruit identification is primarily based on the structure of these three layers.