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botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek w ...
a capsule is a type of simple, dry, though rarely fleshy dehiscent
fruit In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering. Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in particu ...
produced by many species of angiosperms (
flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...
s).


Origins and structure

The capsule (
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
: ''capsula'', small box) is derived from a compound (multicarpeled) ovary. A capsule is a structure composed of two or more
carpel Gynoecium (; ) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more) '' pistils' ...
s. In (flowering plants), the term locule (or cell) is used to refer to a chamber within the
fruit In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering. Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in particu ...
. Depending on the number of locules in the ovary, fruit can be classified as uni-locular (unilocular), bi-locular, tri-locular or multi-locular. The number of locules present in a
gynoecium Gynoecium (; ) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more) ''pistils' ...
may be equal to or less than the number of carpels. The locules contain the
ovule In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the '' integument'', forming its outer layer, the ''nucellus'' (or remnant of the megasporangium), and the ...
s or
seed A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiospe ...
s and are separated by
septa The Southeastern Pennsylvania Transportation Authority (SEPTA) is a regional public transportation authority that operates bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly 4 million people in five c ...
.


Dehiscence

In most cases the capsule is dehiscent, i.e. at maturity, it splits apart (dehisces) to release the
seed A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiospe ...
s within. A few capsules are indehiscent, for example those of ''
Adansonia digitata ''Adansonia digitata'', the African baobab, is the most widespread tree species of the genus '' Adansonia'', the baobabs, and is native to the African continent and the southern Arabian Peninsula (Yemen, Oman). These are long-lived pachycauls; ...
'', '' Alphitonia'', and '' Merciera''. Capsules are often classified into four types, depending on the type and location of dehiscence (see Simpson Fig 9.41 and Hickey & King ). Loculicidal capsules possess longitudinal lines of dehiscence radially aligned with the
locules A locule (plural locules) or loculus (plural loculi) (meaning "little place" in Latin) is a small cavity or compartment within an organ or part of an organism (animal, plant, or fungus). In angiosperms (flowering plants), the term ''locule'' usu ...
, ''i.e.'' not at the septa, along the midrib or dorsal suture (seam) of the locules. If septa are absent, the dehiscence lines lie between the placentae. This type is common among many members of the
Liliaceae The lily family, Liliaceae, consists of about 15 genera and 610 species of flowering plants within the order Liliales. They are monocotyledonous, perennial, herbaceous, often bulbous geophytes. Plants in this family have evolved with a fair a ...
such as
Lilium ''Lilium'' () is a genus of herbaceous flowering plants growing from bulbs, all with large prominent flowers. They are the true lilies. Lilies are a group of flowering plants which are important in culture and literature in much of the world. M ...
(see illustration). Septicidal capsules have dehiscence lines aligned with the sutures of the ovary septa or placentae, that is between the carpels. Both loculocidal and septicidal capsules split into distinguishable segments called valves. The valves are a part of the
pericarp Fruit anatomy is the plant anatomy of the internal structure of fruit. Fruits are the mature ovary or ovaries of one or more flowers. They are found in three main anatomical categories: aggregate fruits, multiple fruits, and simple fruits. Aggr ...
(fruit wall) that has split away, without enclosing the seed or seeds. The borders of the valves may or may not coincide with the borders of carpels. These valves may remain attached to the fruit or fall off. In septicidal capsules the valves remain in place. In some capsules, the split occurs between carpels, and in others each carpel splits open. Circumscissile capsules (pyxide, pyxis, pyxidium or lid capsule) have a transverse, rather than longitudinal, dehiscence line, so that the upper part of the capsule dehisces, usually forming a terminal lid ( operculum) that opens (see illustration). An example is ''
Plantago ''Plantago'' is a genus of about 200 species of flowering plants in the family Plantaginaceae, commonly called plantains or fleaworts. The common name plantain is shared with the unrelated cooking plantain. Most are herbaceous plants, though ...
''. A variant is the Septifragal capsule (valvular capsule) in which the outer walls break away from the septa and (usually axile) placentae as valves. Poricidal capsules dehisce through pores (openings) in the capsule, as in ''
Papaver ''Papaver'' is a genus of 70–100 species of frost-tolerant annuals, biennials, and perennials native to temperate and cold regions of Eurasia, Africa and North America. It is the type genus of the poppy family, Papaveraceae. Description The ...
'', the seeds escaping through these pores. Examples of other plants that produce capsules include
nigella ''Nigella'' is a genus of 18 species of annual plants in the family Ranunculaceae, native to Southern Europe, North Africa, South Asia, Southwest Asia and Middle East. Common names applied to members of this genus are nigella, devil-in-a-bush o ...
,
orchid Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Along with the Asteraceae, they are one of the two largest families of flowerin ...
,
willow Willows, also called sallows and osiers, from the genus ''Salix'', comprise around 400 speciesMabberley, D.J. 1997. The Plant Book, Cambridge University Press #2: Cambridge. of typically deciduous trees and shrubs, found primarily on moist so ...
,
cotton Cotton is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus '' Gossypium'' in the mallow family Malvaceae. The fiber is almost pure cellulose, and can contain minor pe ...
, and jimson weed.


Specialised capsules

Some dry dehiscent fruits form specialised capsule-like structures. A follicle is derived from a single carpel that splits along a suture, as in ''
Magnolia ''Magnolia'' is a large genus of about 210 to 340The number of species in the genus ''Magnolia'' depends on the taxonomic view that one takes up. Recent molecular and morphological research shows that former genera ''Talauma'', ''Dugandiodendro ...
'', while a legume splits along two sutures, and are a defining feature of the Fabaceae. Some variants of legumes that have retained vestigial sutures include loments that split transversely into segments, each with a single seed, and indehiscent legumes, such as ''
Arachis hypogaea The peanut (''Arachis hypogaea''), also known as the groundnut, goober (US), pindar (US) or monkey nut (UK), is a legume crop grown mainly for its edible seeds. It is widely grown in the tropics and subtropics, important to both small and la ...
'' (peanuts). Capsules derived from two carpels include silicles and siliques that dehisce along two suture lines but retain a partition called the replum, which is a septum with attached seeds. While both are characteristic of
Brassicaceae Brassicaceae () or (the older) Cruciferae () is a medium-sized and economically important family of flowering plants commonly known as the mustards, the crucifers, or the cabbage family. Most are herbaceous plants, while some are shrubs. The leav ...
, silicles have a ratio of length to width of no more than 3:1. A
schizocarp A schizocarp is a dry fruit that, when mature, splits up into mericarps. There are different definitions: * Any dry fruit composed of multiple carpels that separate. : Under this definition the mericarps can contain one or more seeds (the m ...
is derived from a compound ovary with two or more locules which then separate radially as one of the above types, such as a schizocarp of follicles, as in ''
Asclepias ''Asclepias'' is a genus of herbaceous, perennial, flowering plants known as milkweeds, named for their latex, a milky substance containing cardiac glycosides termed cardenolides, exuded where cells are damaged. Most species are toxic to humans ...
'' (
Asclepiadoideae The Asclepiadoideae are a subfamily of plants in the family Apocynaceae. Formerly, they were treated as a separate family under the name Asclepiadaceae, e.g. by APG II, and known as the milkweed family. They form a group of perennial herbs, twi ...
) (see illustration). A
mericarp A schizocarp is a dry fruit that, when mature, splits up into mericarps. There are different definitions: * Any dry fruit composed of multiple carpels that separate. : Under this definition the mericarps can contain one or more seeds (the m ...
is a portion of the fruit that separates from the ovary to form a distinct locule unit which encloses the seed, usually-nut-like, as in
Apiaceae Apiaceae or Umbelliferae is a family of mostly aromatic flowering plants named after the type genus '' Apium'' and commonly known as the celery, carrot or parsley family, or simply as umbellifers. It is the 16th-largest family of flowering plan ...
in which the mericarps are joined by a stalk (carpophore). Thus a schizocarp of mericarps is a structure in which the carpels of a single ovary split to form mericarps. A schizocarp of nutlets is derived from a carpel that becomes lobed, and the lobes become nutlets that split apart. Examples include
Boraginaceae Boraginaceae, the borage or forget-me-not family, includes about 2,000 species of shrubs, trees and herbs in 146, to 156 genera with a worldwide distribution. The APG IV system from 2016 classifies the Boraginaceae as single family of the or ...
and most Lamiaceae, where the styles are attached between the ovary lobes.


Nuts

Capsules are sometimes mislabeled as nuts, as in the example of the
Brazil nut The Brazil nut (''Bertholletia excelsa'') is a South American tree in the family Lecythidaceae, and it is also the name of the tree's commercially harvested edible seeds. It is one of the largest and longest-lived trees in the Amazon rainforest. ...
or the
Horse-chestnut ''Aesculus hippocastanum'', the horse chestnut, is a species of flowering plant in the maple, soapberry and lychee family Sapindaceae. It is a large, deciduous, synoecious (hermaphroditic-flowered) tree. It is also called horse-chestnut, Europe ...
. A capsule is not a nut because it releases its seeds and it splits apart. Nuts, on the other hand, do not release seeds as they are a compound ovary containing both a single seed and the fruit. Nuts also do not split. In the Brazil nut, a lid on the capsule opens, but is too small to release the dozen or so seeds (the actual "Brazil nut" of commerce) within. These germinate inside the capsule after it falls to the ground.


See also

*
Fruit In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering. Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in particu ...


References


Bibliography

* * *
Encyclopædia Britannica online


{{Use dmy dates, date=April 2017 Fruit morphology Orchid morphology