Northern Ontario Plant Database
A fruit is defined as a mature ovary and associated floral parts. The fruit wall is called a pericarp and is composed of three layers: the outer layer, or exocarp, the middle layer, or mesocarp, and the inner layer, or endocarp.
Fruits are classified according to several basic characters:
- the number of flowers, carpels, or inflorescences that make up the fruit,
- whether or not the fruit is derived from just an ovary, or is floral tissue, like the hypanthium, part of the fruit,
- the texture of the pericarp layers, and
- how the fruits release their seeds.
The first type of category is determined by how many flowers or carpels are involved in the formation of each fruit and whether or not the fruit includes floral parts other than the ovary:
- simple fruits - fruits derived from a single flower with 1 pistil (e.g., grape).
- accessory fruits - fruits derived from flowers with a hypanthium or enlarged receptacle (e.g., apple).
- aggregate fruits - fruits derived from a single flower with several, separate pistils attached to a common receptacle (e.g. raspberry).
- multiple fruits - fruits derived from an entire inflorescence; individual flowers are tightly packed and fuse together as the fruit develops (e.g., pineapple). Fruits derived from several ovaries, as in multiple and aggregate fruits, are also called syncarps if the individual ovaries fuse into a single fruit.
Next we see whether the fruit has a fleshy pericarp or a dry pericarp:
- fleshy fruits - fruits with a thin exocarp surrounding a fleshy mesocarp and/or endocarp.
- dry fruits - fruit with a dry or woody periderm, which can be rather thin and easy to break, fibrous, or hard and stony.
Finally, we look at how the fruit releases its seeds.
- dehiscent fruits - fruits that split open to release their seeds.
- indehiscent fruits - fruits that stay closed and only release their seeds through physical breakdown or decomposition of the fruit.
The classification of fruits presented here follows Radford et al. (1974). Other classification systems for fruits have been developed recently (Spjut 1994), but the system used by Radford is more widely accepted. For more information on the major fruit groups, see this article on fruit types from Wayne's Word.