Category: 3. Fruits

Several of many flowers in a single inflorescence will develop into a multiple fruit. The flowers develop separately into fruitlets on their own receptacles, but at maturity, they will cluster together and develop into a larger single fruit. Pineapples and figs are good examples, although the fig develops from a unique “outside-in” inflorescence.

Accessory fruits

Accessory fruit is a kind of fruit that contains tissue derived from plant parts other than the ovary. Strawberry is an example of an accessory fruit.

These fruits come from a single flower with multiple pistils. The individual pistils start as tiny drupes or other fruitlets, but at maturity, they cluster on a single receptacle. Examples are strawberries, raspberries, and blackberries.

Fruits may be classified based on the arrangement from which they derive: (1) simple fruits, (2) aggregate fruits, (3) multiple fruits,

Simple fruits

Simple fruits are fruits that develop from a single or compound ovary with only one pistil (of a single flower). Simple fruits may either be fleshy or dry.

Fleshy Fruits

Fleshy fruits have a mesocarp that is at least partially fleshy at maturity. The ovary may be simple, meaning derived from one modified leaf called a carpel, or compound. The ovary also may be superior or inferior and may develop into a fruit with or without other flower parts integrated.

• Drupe— Drupes are simple fleshy fruits with one seed encased in a stony pit. Usually, the ovary is a superior ovary with one ovule. The stone fruits—cherries, peaches, olives, apricots, and almonds—are examples. Although not readily recognized as a fleshy fruit, coconuts are drupes. The husk is the mesocarp and exocarp which is generally removed before making it to the market. The pit with the watery seed endosperm is what we see piled up at the store.

• Berry—These develop from a compound ovary and usually contain multiple seeds. It is difficult to determine the three regions. This group is broken down further into three types of berries:
  True berries are fruits with a thin skin and a pericarp. They are generally soft at maturity and usually have multiple seeds although dates and avocados are notable exceptions. Some berries have incorporated flower parts which can be seen in remnant as scars. Examples are tomatoes, grapes, peppers, blueberries, cranberries, bananas, and eggplants. Note that botanically speaking raspberries, strawberries and blackberries are not berries. Pepos are berry fruits with thick rinds. They have multiple seeds and include pumpkins, watermelons, cantaloupes, and squashes. Finally, the hesperidium is a leathery skinned berry that contains oils. Saclike outgrowths of the inner ovary wall become filled with juice as the ovary matures. All members of the Citrus Family produce hesperidium fruits.
• Pome—The majority of the flesh in pomes comes from the swollen receptacle that grows up and around the ovary (inferior ovary). The seeds are encased by a leathery or papery endocarp. Apples are good examples. The apple core is the ovary with seeds and the rest is an overgrowth of the receptacle. (Sometimes these fruits that are derived from more than the ovary are called accessory fruits.) Examples of pomes include apples, pears, and quinces.

Dry fruits

Dry fruits have a mesocarp that is dry at maturity. Dry fruits that split at maturity distinguished by the way in which they split:

• Follicle—Splits along one side or one seam. Ex: larkspur, milkweed
• Legume—Splits along two sides or seams. Ex: Peas, beans, kudzu, peanuts, carob
• Silique—split along two sides or seams, the difference from legumes is that the seeds are carried on a central partition which is exposed upon splitting. Ex: Mustard Family, including broccoli, cabbage, radish, watercress
• Capsule—Most common of splitting dry fruit. Composed of two carpels and split in a variety of ways: along carpel partitions, through carpel cavities, pores, or via a cap that pops off to release seeds. Ex: irises, poppies, orchids, violets, and snapdragons.

Dry fruits that do not split at maturity: the single seed is more or less united with the pericarp.

Other kinds of dry fruits are as follows:

• Achene—the seed is attached to the pericarp (husk in this case) only at the bottom and can be separated easily. Ex: sunflower seeds (husk, plus edible seed constitutes the achene), buttercup, and buckwheat.
• Nut—the pericarp of nuts are generally harder than the achenes, although they are otherwise quite similar in structure. Nuts develop with a cup or cluster or bracts at their base. Ex: hazelnuts, hickory nuts, and chestnuts. Note that botanically speaking most things called ‘nuts’ are not nuts such as peanuts (legume), coconuts, almonds, walnuts, pecans (all drupes) Brazil nuts (capsule) and pistachios (drupes). Yet another misnomer commonly accepted.
• Grain—Grains are all of the Grass Family and feature a pericarp that cannot be separated from the seed. Ex. Corn, wheat, barley, rice, and oats. The grains are also called caryopses.
• Samara—pericarp extends as a wing or membrane which aids in dispersal. Usually, samaras are produced in pairs, although elms and ash trees produce them singly. These are the ‘helicopters’ that I am certain we all have played with at one point or another. Ex: maple trees
• Schizocarp—schizocarps are the twin fruits, as at maturity the fruit dries out and breaks into two one-seeded segments. Ex: carrots, dill, parsley, and anise.

A fruit, ripened ovary, has three major regions that are sometimes difficult to distinguish from each other. The outer layer, sometimes referred to as the skin, is actually called the exocarp. The mesocarp is the fleshy portion that is usually eaten when consuming fruit. The endocarp is the innermost boundary around the seed. Sometimes the endocarp is hard and stony such as a peach pit that surrounds the seed. The endocarp can also be papery as in apples, where it is barely visible in cross-section. All three of these regions; the exocarp, mesocarp, and endocarp, are collectively called the pericarp. The pericarp can be quite thin, as is the case with dry fruits.

Some fruits have flower parts modified or fused to the ovary at maturity. Fruits are classified according to features at maturity: fleshy, dry, split exposing seeds, non-splitting, one ovary or multiple ovaries. We will go through these various classifications and see what examples fall into the various categories.

The fruit is a mature or ripened ovary that usually contains seeds. In contrast, a vegetable can consist of leaves (lettuce, cabbage), leaf petioles (celery), specialized leaves (onions), stems (white potato), stems and roots (beets), flowers and their peduncles (broccoli), flower buds (globe artichokes) and or other parts of the plant. The fruit is by definition just the ovary part of a flower, therefore all fruits come exclusively from flowering plants.