I. Simple Fruits: A single ripened ovary from a single flower.
A. Fleshy Fruits: All of most of the ovary wall (pericarp) is soft or fleshy at maturity.
1. Berry: Entire pericarp is fleshy, although skin is sometimes tough; may be one or many seeded. E.g. grape, tomato, papaya, pomegranate, sapote, persimmon, guava, banana and avocado. The latter two fruits are often termed baccate (berry-like). The banana fruit is a seedless, parthenocarpic berry developing without pollination and fertilization. In the pomegranate, the edible part is the fleshy layer (aril) around each seed. For photos of many of these berries, look them up by their common name in the Wayne's Word Index. According to Spjut (1994), the pepo is not limited to the gourd family (Cucurbitaceae). The papaya (Carica) is a pepo because of its thick outer rind. He also considers the banana (Musa) to be pepo. The pomegranate has a persistant calyx and endocarp reminiscent of a pome, and membranous partitions, juicy seed vesicles, and a leathery exocarp similar to a hesperidium. Spjut classifies the pomegranate as a "balusta." Berry-like fruits, such as the avocado (Persea) and kiwi (Actinidia) are called a "bacca."
2. Pepo: Berry with a hard, thick rind; typical fruit of the gourd family (Cucurbitaceae). E.g. watermelon, cucumber, squash, cantelope and pumpkin.
3. Hesperidium: Berry with a leathery rind and parchment-like partitions between sections; typical fruit of the citrus family (Rutaceae). E.g. orange, lemon, grapefruit, tangelo and kumquat.
4. Drupe: Fleshy fruit with hard inner layer (endocarp or stone) surrounding the seed. E.g. peach, plum, nectarine, apricot, cherry, olive, mango and almond. Some botanists also include the fruits of walnuts, pecans, date palms, macadamia nuts, pistachio nuts, tung oil and kukui nuts as drupes because of their outer, green, fleshy husk and stony, seed-bearing endocarp. These latter fruits are also called drupaceous nuts. The coconut is considered a dry drupe with a green, waterproof outer layer (exocarp), a thick, buoyant, fibrous husk (mesocarp) and a hard, woody, inner layer (endocarp) surrounding the large seed. The actual seed embryo is embedded in the coconut meat (endosperm). Nutrient-rich coconut milk is liquid endosperm that has not formed firm tissue with cell walls. According to Spjut (1994), the fruit of a coconut (Cocos) is a "nucleanium." [There is considerable disagreement among authorities about the classification of some of these fruits. For example, the California Macadamia Society considers the macadamia nut to be a follicle. See section B-1 below under dry, dehiscent fruits.]
Note: A number of so-called nuts are probably better placed in the drupe category. This is especially true of the walnut family (Juglandaceae), although some older references still consider these fruits to be nuts. In hickory & pecan (Carya) the outer husk or shuck splits into four valves, exposing the hard, indehiscent nut . According to many botanists, the outer husk is part of the pericarp, and the hard, inner layer surrounding the seed is the endocarp; therefore, these fruits are technically drupes or drupaceous nuts. Walnut & butternut (Juglans), two additional members of the walnut family (Juglandaceae), have similar drupe-like fruits. The outer green husk resembles the outer pericarp (exocarp and mesocarp) of a drupe. For this reason, walnuts are sometimes referred to as dry drupes, and the hard shell surrounding the seed is considered to be the endocarp layer as in coconuts. In true nuts, the hard, indehiscent layer surrounding the seed is the entire ovary wall or pericarp, and the outer husk is composed of involucral tissue that is not part of the ovary wall or pericarp. According to most botanical references, the outer green layer (husk) of the walnut is part of the pericarp and the hard shell surrounding the seed is really the endocarp. Therefore, walnuts and pecans probably fit the dry drupe category rather than a true nut. Some authors elegantly avoid this dilemma by calling these fruits drupe-like or "drupaceous nuts."
According to "The Morphology of the Flowers of the Juglandaceae" by W.E. Manning (1940),American Journal of Botany 27 (10): 839-852, the fruits of Juglans and Carya are drupe-like but not a true drupe or dry drupe. The fruit is sometimes called a "tryma" but can be described as a nut. Webster's Third New International Dictionary describes a tryma as a nutlike drupe (as the fruit of the walnut or hickory) in which the epicarp (exocarp) and mesocarp separate as a somewhat fleshy or leathery rind from the hard 2-valved endocarp. According to Spjut (1994), the walnut (Juglans) is a pseudodrupe and the pecan (Carya) is a "tryma."
5. Pome: Ovary or core surrounded by edible, fleshy receptacle tissue (hypanthium or fleshy floral tube) that is really not part of the pericarp. The actual ovary or core is usually not eaten, at least by most humans. This is typical fruit of certain members of the rose family (Rosaceae), including apple, pear, quince and loquat.
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B. Dry Fruits: Pericarp dry at maturity.
1. Dehiscent Dry Fruits: Pericarp splits open along definite seams.
a. Legume: An elongate "bean pod" splitting along two seams; typical fruit of the third largest plant family, the legume family (Leguminosae or Fabaceae). The pod represents one folded modified leaf or carpel that is fused along the edges. E.g. black locust, redbud, acacia, coral tree, orchid tree, wisteria and many more genera. Note: Some legume fruits are indehiscent, including the carob tree, mesquite and honey locust. In addition, some legume fruits are oblong, rounded, kidney-shaped (reniform), or coiled (spiral-shaped), such as sweet clover (Melilotus alba and M. officinalis), black medic (Medicago lupulina), bur clover (M. polymorpha) and alfalfa (M. sativa). Some specialized legume fruits (called loments) break apart into indehiscent one-seeded joints. A good example of a loment is the very effective hitchhiker called stick-tights or beggar's-ticks (Desmodium cuspidatum).
b. Silique: A slender, dry, dehiscent fruit that superficially resemble a legume, except the mustard silique is composed of two carpels with a partition or septum down the center (i.e. between the two carpels or valves). [The legume fruit is composed of a single carpel and does not have the central partition or septum.] This is the typical fruit of the mustard family (Cruciferae or Brassicaceae). E.g. field mustard, turnip and cabbage (Brassica species), stock (Mathiola), wallflower (Erysimum) and London rocket (Sisymbrium). The silicle is a shortened (less elongate) version of a silique, including sweet alyssum (Lobularia), peppergrass (Lepidium) and shepherd's purse (Capsella). [Note: As with legumes there are a few exceptions to the typical form of siliques and silicles. In wild radish (Raphanus) the silique does not split lengthwise, but instead it breaks transversely into several seed-bearing joints. In lace pod (Thysanocarpus) the silicles are indehiscent.]
c. Capsule: Seed pod splits open is various ways and usually along several definite seams. Capsules typically split open into well-defined sections or carpels which represent modified leaves. This is a very common dry fruit found in many different plant families. E.g. Catalpa,Jacaranda, Pittosporum, Aesculus, Agave, Yucca, Eucalyptus, devil's claw (Proboscidea), floss silk tree (Chorisia), kapok tree (Ceiba) and castor bean (Ricinus communis). Capsules may split open along the locules (loculicidal), along the septa (septicidal), through pores (poricidal), or the entire top of the capsule separates as a single lid-like section (circumscissile). A common landscaping tree in southern California called the golden-rain tree (Koelreuteria) produces bladder-like capsules that are loculicidally dehiscent into three valves. The opium poppy (Papaver somniferum) produces a classic poricidal capsule in which the tiny seeds fall out of the pore-like windows as the capsule shakes in the wind. The edible weed called purslane (Portulaca) has a many-seeded circumscissile capsule. The Mexican jumping bean (Sebastiana pavoniana) produces a 3-carpellate capsule, each carpel bearing a seed. Sometimes the carpel is occupied by a special moth larva that eats the seed and moves its one-room carpel container by contorting and hurling its body. In the liquidambar tree (Liquidambar styraciflua) the globose fruiting heads are composed of numerous tiny capsules, each bearing one or two winged seeds and a number of aborted ovules (immature seeds). It should be noted here that some capsules are indehiscent. Their carpels do not separate and release the seeds. Two examples of plants with indehiscent capsules are the South African baobab tree (Adansonia digitata) and two species of South African gardenias (Gardenia thunbergii and G. volkensii). The seed pods of South African gardenias are chewed opened by large herbivores, and the seeds are dispersed in their feces. Spjut (1994) classifies the unusual fruit of the devil's claw (Proboscidea) as a "ceratium," a capsular fruit that opens by a separation or break in the pericarp layers.
d. Follicle: A single ripened ovary (representing a single modified leaf or carpel) that splits open along one seam. The follicle may occur singly (as in milkweed) or in clusters: two in oleander, 2-5 in peony, 3 in larkspur, 5 in columbine and 4-5 in bottle tree (Sterculia or Brachychiton). The cone-like fruit of the magnolia tree is an aggregate of many small follicles, each containing a single bright red seed. The term apocarpous refers to flowers with separate and distinct carpels, such as delphiniums and columbines of the buttercup family (Ranunculaceae). Although it also belongs to the buttercup family, the fused (syncarpous) carpels of Nigella form a many-seeded capsule.
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2. Indehiscent Dry Fruits: Pericarp does not split open. These fruits usually contain only one seed.
a. Achene: Very small, one-seeded fruit, usually produced in clusters. At maturity the pericarp is dry and free from the internal seed, except at the placental attachment. This is the typical fruit of the largest plant family, the sunflower family (Compositae or Asteraceae). Examples of this type of fruit include the sunflower (Helianthus), buttercup (Ranunculus) and sycamore (Platanus). In the sycamore, the globose fruiting heads are composed of tiny, one-seeded achenes interspersed with hairs (some authors refer to these individual fruits as nutlets). [The globose heads of the liquidambar tree are actually composed of numerous tiny capsules.]
b. Anthocarp: In the four o'clock family (Nyctaginaceae), individual apetalous flowers have a tubular, petaloid calyx that resembles a sympetalous corolla. The lower portion of the calyx tightly enwraps the one-seeded achene and is persistent around the fruit as an anthocarp. The calyx base plus the enclosed seed-bearing achene is the unit of dispersal. In some members of the Nyctaginaceae, the persistent calyx base bears sticky glandular projections that aid in dispersal by adhering to the bodies of animals. This is especially true in pisonia trees (Pisonia umbellifera) in which the numerous glutinous anthocarps stick to the feathers of seabirds. This is an effective method of dispersal to distant atolls and islands of the South Pacific region. Sometimes a hapless seabird is completely covered by clusters of the sticky anthocarps, to the point where flight is difficult or impossible. Unable to remove the water-resistant, glue-like anthocarps from its feathers, the seabird drowns in the surf and is consumed by ravenous beach crabs.
c. Grain or Caryopsis: A very small, dry, one-seeded, indehiscent fruit in which the actual seed coat is completely fused to the ovary wall or pericarp. The outer pericarp layer or husk is referred to as the bran, while the inner, seed layer is called the germ. This is the characteristic fruit of the large grass family (Gramineae or Poaceae). The grain is truly a fruit (not a seed) because it came from a separate ripened ovary within the grass inflorescence. This is the number one source of food for people on the earth. E.g. Corn (maize), wheat, rice, rye, barley, oats, Johnson grass, Bermuda grass and many more species. In corn grains, the main white material that explodes when the grains are heated is endosperm tissue within the seed. Pressure (water vapor) builds up within the grains until they literally explode.
d. Schizocarp: A small dry fruit composed of two or more sections that break apart; however, each section or carpel (also called a mericarp) remains indehiscent and contains a single seed. Because the seed-bearing sections or carpels (called mericarps) do not split open, this type of fruit is usually placed under indehiscent dry fruits. This is the characteristic fruit of the carrot family (Umbelliferae or Apiaceae). E.g. Carrot (Daucus), celery (Apium) and sweet fennel (Foeniculum vulgare). Other examples of schizocarps include filaree or stork's bill (Erodium) and cheeseweed (Malva), two common weeds in southern California. In these weeds, the seed-bearing carpels (mericarps) separate from each other, but remain indehiscent. Gynoecium is a collective term for the carpels of a flower. Biologists commonly refer to this floral unit as a pistil. Monocarpous flowers are composed of one carpel (a simple pistil). The terms apocarpous and syncarpous refer to compound pistils composed of more than one carpel. Apocarpous flowers contain two or more distinct carpels. In syncarpous flowers, two or more carpels are fused together. In cheeseweed, the carpels are attached to a central, conical connection stalk, but separate from this stalk at maturity. Some authors consider the fruit of the maple (Acer) to be a schizocarp because it splits into two indehiscent, seed-bearing carpels; however, because of the wing on each seed-bearing carpel, other botanists refer to maple fruits as double samaras (see the samara fruit).
One of the most painful schizocarps is the puncture vine (Tribulus terrestris). When dry, the spiny fruit splits into indehiscent, seed-bearing sections (carpels). The spines of each section are arranged so that one is always facing upward, like the medieval weapon called a caltrop. The spiny, seed-bearing burs readily penetrate bare feet, shoes and rubber tires.
e. Samara: Small, winged, one-seeded fruit, usually produced in clusters on trees. E.g. Maple (Acer): a double samara, ash (Fraxinus), elm (Ulmus) and tree of heaven (Ailanthus). Samaras resemble the winged seeds of a pine, but they are truly one-seeded fruits with a pericarp layer surrounding the seed. The leguminous tipu tree (Tipuana tipu) has a winged fruit that certainly resembles a samara even though it belongs to the legume family (Leguminosae or Fabaceae). Like auto-rotation of helicopters, the samaras spin as they sail through the air, an effective method of dispersal. Richard Spjut (1994) classifies some of the larger winged fruits ofShorea (Diptocarpaceae) and Gyrocarpus (Hernandiaceae) as a "pseudosamara."
 Whirling Nut (Gyrocarpus)
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f. Nut: Larger, one-seeded fruit with very hard pericarp, usually enclosed in a husk or cup-like involucre. Unfortunately, the above reference by Richard Spjut does not use the term "nut" as a distinct fruit type.
(1) Acorn of oak (Quercus): The actual nut sits in a cup-shaped involucre of imbricate (overlapping) scales. Classified as a "glans" by Richard Spjut (1994).(2) Chestnut (Castanea), beech (Fagus) & chinquapin (Castanopsis): One or more nuts sit in a spiny, cup-shaped involucre. Classified as a "trymosum" by Richard Spjut (1994).
(3) Hazelnut or filbert (Corylus): Nut sits in a leafy (C. americana) or tubular (C. cornuta) involucre. Classified as a "diclesium" by Richard Spjut (1994).
(4) Walnut (Juglans) and pecan (Carya) are placed in the drupe category (section A-4) above, although some botanists maintain that they are true nuts. In true nuts, the hard, indehiscent layer surrounding the seed is the entire ovary wall or pericarp, and the outer husk is composed of involucral tissue that is not part of the ovary wall or pericarp. According to most botanical references, the outer green layer (husk) of the walnut is part of the pericarp and the hard shell surrounding the seed is really the endocarp. Therefore, walnuts and pecans probably fit the dry drupe category rather than a true nut. Other authorities claim that the walnut husk is composed of involucral tissue, perianth and an outer layer of pericarp, but is not totally derived from the pericarp. However, since the walnut husk contains pericarp tissue (at least in part), and is not entirely derived from involucral (non-pericarp) tissue, Wayne's Word considers the walnut to be drupaceous rather than a true, undisputed nut. Remember that scientific knowledge is constantly being scrutinized and changed, and the exact classification of dubious, borderline fruits such as the walnut are open for review and modification. The walnut is classified as a "pseudodrupe" by Richard Spjut (1994). See discussion about walnuts under drupes (section A-4 above).Note: Brazil nuts are seeds produced in a large, woody capsule. Cashews are nuts with a hard shell that is removed before shipment to food stores. The cashew "nut" (drupaceous nut) is produced at the summit of a fleshy receptacle called the "cashew apple." Pine nuts are actually gymnosperm seeds produced in a woody, ovuliferous seed cone. The peanut (Arachis hypogea) is actually a seed with a papery seed coat, typically two seeds enclosed in a dehiscent pod called a legume. After fertilization, the flower stalk of the peanut curves downward, and the developing fruit (legume) is forced into the ground by the proliferation and elongation of cells under the ovary. The peanut pod subsequently develops underground. For more fruits called "nuts" refer to the above section A-4 about drupes and drupaceous nuts.
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g. Utricle: Small, bladderlike, thin-walled, one-seeded, indehiscent fruit. Although it is seldom seen by casual observers, this is the characteristic fruit of the duckweed family (Lemnaceae). The dehiscent one-seeded fruits of Amaranthus (Amaranthaceae) are often called circumscissile utricles because the top half of the fruit separates, exposing a shiny black seed.
Note: Wayne's Word contains a lot of additional information about the remarkable duckweed family (Lemnaceae), the undisputed world's smallest flowering plants. Just click on the green Lemnaceae tab for a complete index to articles and photos. |
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II. Aggregate Fruits: A cluster or aggregation of many ripened ovaries (fruits) produced from a single flower. In blackberries and raspberries (Rubus), the individual fruits are tiny, one-seeded drupes or drupelets. Since all the seed-bearing ovaries (carpels) form a fused cluster, the fruit is also called a syncarp. In strawberries (Fragaria), the individual fruits are tiny, one-seeded achenes imbedded in a sweet, fleshy receptacle. Another term for an aggregate cluster of ovaries all derived from a single flower is the "etaerio." In fact, a rose hip (Rosa) eaten as an entire fruit could be considered an etaerio of achenes enclosed by a fleshy receptacle. Fruits of the genus Annona (Annonaceae), including the sugar apple (A. squamosa), cherimoya (A. cherimola), custard apple (A. reticulata) and soursop (A. muricata) resemble large fleshy berries with scales or projections on the outer surface. They are actually composed of many ovaries fused together and are technically aggregate fruits called syncarps. They are not multiple fruits because they develop from a single flower bearing many pistils (carpels).
III. Multiple Fruits: A cluster of many ripened ovaries (fruits) produced by the coalescence of many flowers crowded together in the same inflorescence, typically surrounding a fleshy stem axis. E.g. mulberry, osage orange, pineapple, breadfruit and jackfruit. In the mulberry (Morus), the individual fruits are tiny drupes called drupelets. In the pineapple (Ananas), the individual fruits are berries imbedded in a fleshy, edible stem, each berry subtended by a jagged-edged bract where the original flower was attached. The fleshy spadix of Monstera deliciosa is also a multiple fruit because it is derived from numerous, tightly-packed female flowers. Another term for multiple fruits composed of a fleshy spike or raceme of tightly packed ovaries is the sorosis.
Note: Fig trees (Ficus) produce an edible multiple fruit called a syconium. It is a fleshy, flask-shaped structure (inflorescence) lined on the inside with numerous female flowers, each forming a tiny, one-seeded drupelet. Seed formation requires a symbiotic wasp that enters the syconium and pollinates the female flowers. Smyrna and California-grown Calimyrna figs require wasp pollination. Other fig varieties will produce edible, seedless, parthenocarpic syconia without pollination. This is a very complex and fascinating story that is discussed in several Wayne's Word articles. Look up "fig" under the blue index tab for more information.
Miscellaneous Notes On Fruit Types: Some trees produce seeds and pollen in separate inflorescences called catkins or aments. This includes monoecious species with both male and female catkins on the same tree; and dioecious species with separate male and female trees. In birch (Betula) and alder (Alnus), the seeds (nutlets) are produced in a woody, cone-like catkin. In other trees, such as oak (Quercus), only pollen is produced in the catkins.
In true cone-bearing trees, the immature seeds (ovules) are borne at the surface of ovuliferous scales instead of enclosed within an a ovary as in flowering plants. Because the ovules are exposed to the wind-blown pollen during the pollination period, these trees are referred to as gymnosperms (which means naked seeds). The ovuliferous scales collectively form a woody seed cone sealed with sticky resin. At maturity (in one or two years depending on the species), the scales dry and separate from each other, thus releasing the winged seeds. In junipers (Juniperus) the scales are fleshy and fused together, and the seed cones superficially resemble berries. In the maidenhair tree (Ginkgo biloba), fern pine (Podocarpus), and the California nutmeg (Torreya californica), the large seed with a fleshy outer coat is borne naked on the branchlets. In the yew tree (Taxus) the naked seed is borne in a fleshy, cup-like structure called an aril.
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