From Flower to Fruit: The Basic Idea
When a flower is pollinated, the ovary begins to swell and ripen into a fruit. The wall of the ovary becomes the pericarp — which itself has three layers: the outer epicarp, the middle mesocarp, and the inner endocarp. In a mango, the epicarp is the skin, the mesocarp is the juicy flesh, and the endocarp is the hard stone around the seed.
Most fruits you know — a mango, a plum, a tomato — come from a single ovary of a single flower. That's a simple fruit. But nature doesn't always follow the simple path. Sometimes, many ovaries fuse together. Sometimes, the whole inflorescence (a cluster of flowers) contributes to what we call a fruit. That's where aggregate and composite fruits come in.
Aggregate Fruits: Many Ovaries, One Flower
Imagine a single flower that has many separate ovaries (a condition called apocarpous gynoecium). After fertilisation, each ovary develops into a tiny fruitlet. All these fruitlets sit together on the same receptacle, forming one fruit that looks like a cluster.
An aggregate fruit develops from a single flower with multiple free ovaries. Each ovary becomes a small fruitlet, and the whole cluster is the fruit.
The classic example is the strawberry. What you eat is the swollen, fleshy receptacle. The tiny "seeds" on the surface are actually the individual fruitlets — each is a small achene (a dry, one-seeded fruit). Another example is raspberry: each little bump is a drupelet (a tiny stone fruit) that came from one ovary of the same flower.
To tell if a fruit is aggregate: look for a single flower stalk (pedicel) and a cluster of small, seed-like units on a common base. If each unit has its own seed, it's likely aggregate.
Composite Fruits: Many Flowers, One Fruit
Now take it a step further. Instead of one flower, consider a whole inflorescence — a cluster of many flowers. After fertilisation, the entire inflorescence, along with its bracts and receptacle, fuses into a single fruit-like structure. This is a composite fruit (also called a multiple fruit or sorosis).
A composite fruit develops from an entire inflorescence (many flowers), not just one flower. The whole cluster ripens into one unit.
The most familiar example is the pineapple. The "fruit" you buy is actually the fused ovaries, bracts, and the axis of the inflorescence. Each hexagonal "eye" on the surface corresponds to one flower. Another is the jackfruit — the large, spiky structure is a composite fruit where the fleshy parts are the perianths of many flowers fused together. Fig is a special case: the flowers are inside a hollow receptacle, and the "fruit" is that receptacle with all the tiny fruitlets inside.
Do not confuse "composite" with "aggregate". Aggregate = one flower, many ovaries. Composite = many flowers, many ovaries. The difference is the number of flowers involved.
True Fruits vs. False Fruits
This distinction cuts across all fruit types.
A true fruit develops only from the ovary. The pericarp is the only part that becomes the fruit. A mango, a tomato, a grape — all true fruits. …