Fruits are produced only by flowering plants (angiosperms). Following pollination of the flower, the fertilized ovules develop into seeds while the surrounding ovary wall forms the fruit tissue, or pericarp.

Types of Fruits

The botanical definition of a fruit is an organ that contains seeds, protecting these as they develop and often aiding in their dispersal. This may be at odds with everyday usage of the word "fruit." Botanically, pineapples, oranges, and apples are fruits, but so too are "vegetables" like tomatoes and cucumbers. The pods that contain peas and beans are fruits, as are the dry, inedible structures that bear the seeds of many wild plants.

MAJOR FRUIT TYPES Type Definition Examples SIMPLE From a single pistil DRY INDEHISCENT At maturity dry; does not split open Achene Close-fitting pericarp surrounding a single seed Sunflower Grain Close-fitting pericap fused to a single seed Corn, wheat Nut Thick, woody pericarp surrounding a single seed Walnut, hazelnut DRY DEHISCENT At maturity dry and splits open Legume Pod that splits along two opposite sides Beans, peas Capsule Fruit opening by several splits or pores Cotton, poppy Schizocarp Fruit splitting into 1-seeded segments Dill FLESHY Mostly fleshy at maturity; do not usually split open Drupe 1- to 2-seeded; the innermost pericarp layer, stony and enclosing the seed(s) Plum, peach Berry 1- to many-seeded; no stony innermost layer of pericarp Tomato, grape, (all citrus fruit are berries of a special type termed a hesperidium) AGGREGATE Formed by fusion of several separate pistils of one flower Raspberry, cherimoya MULTIPLE Formed by fusion of several separate pistils of several grouped flowers Pineapple, fig

There are many ways to classify fruits, but the simplest distinction is between fleshy and dry fruits. Fleshy fruits are made of living cells and are often juicy and sweet (oil-rich olives and avocados are exceptions). Dry fruits at maturity are made up of dead cells and are divided into those that split open (dehiscent fruit) and those that do not (indehiscent fruit). Within these broad categories many specialized fruit types are recognized. Nuts (for example, hazelnuts and pecans) are one such category, defined as dry, indehiscent fruits with a hard, stony wall. Everyday usage of the word "nut" is, however, quite different, and includes cashew nuts and peanuts (which are actually seeds not fruits).

True fruits are formed by the ovary, which is the lower region of the pistil and the female sex organ of the flower. Sometimes the bulk of the fruit is not derived from the ovary but from some other part(s) of the flower. Such fruits are termed false fruits or accessory fruits. Strawberry is a good example of this. The fleshy tissue people consider the fruit is derived from the receptacle (the swollen tip of the flower stalk), and the true fruits are the tiny, seedlike achenes on the surface.

Apart from strawberry, all the fruit types discussed so far are simple fruits derived from single pistils. In contrast to simple fruits are aggregate and multiple fruits, which are formed from many pistils and, in turn, many

ovaries. Aggregate fruits like raspberries and blackberries are formed from the several ovaries of a single flower. Multiple fruits like pineapples and mulberries develop from the fusion of the ovaries of several flowers. Interest-ingly, some fruits (such as banana) develop without seed formation, a phenomenon termed parthenocarpy.