botany Botany, also called plant science, is the branch of natural science and biology studying plants, especially Plant anatomy, their anatomy, Plant taxonomy, taxonomy, and Plant ecology, ecology. A botanist or plant scientist is a scientist who s ...

, a capsule is a type of

simple Simple or SIMPLE may refer to: *Simplicity, the state or quality of being simple Arts and entertainment * ''Simple'' (album), by Andy Yorke, 2008, and its title track * "Simple" (Florida Georgia Line song), 2018 * "Simple", a song by John ...

, dry, though rarely fleshy

dehiscent Dehiscence is the splitting of a mature plant structure along a built-in line of weakness to release its contents. This is common among fruits, anthers and sporangia. Sometimes this involves the complete detachment of a part. Structures that op ...

fruit In botany, a fruit is the seed-bearing structure in flowering plants (angiosperms) that is formed from the ovary after flowering. Fruits are the means by which angiosperms disseminate their seeds. Edible fruits in particular have long propaga ...

produced by many species of angiosperms (

flowering plants Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

Origins and structure

The capsule (

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

: ''capsula'', small box) is derived from a compound (multicarpellary)

ovary The ovary () is a gonad in the female reproductive system that produces ova; when released, an ovum travels through the fallopian tube/ oviduct into the uterus. There is an ovary on the left and the right side of the body. The ovaries are end ...

. A capsule is a structure composed of two or more

carpel Gynoecium (; ; : gynoecia) 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 ...

s. In (flowering plants), the term

locule A locule (: locules) or loculus (; : loculi) 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'' usually refers to a chamber within an ovary ...

(or cell) is used to refer to a chamber within the

. 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 (; ; : gynoecia) 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 (botany), whorl of a flower; it consists ...

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 sporangium, megasporangium), ...

s or

seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...

s and are separated by

septa SEPTA, the Southeastern Pennsylvania Transportation Authority, is a regional public transportation authority that operates bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly four million people througho ...

Dehiscence

In most cases the capsule is

, i.e. at maturity, it splits apart (dehisces) to release the

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; rad ...

'', '' 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 ). Lilium candidum MHNT

Loculicidal capsules possess longitudinal lines of dehiscence radially aligned with the

locules A locule (: locules) or loculus (; : loculi) 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'' usually refers to a chamber within an ovary ( ...

, ''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 Placentation is the formation, type and structure, or modes of arrangement of the placenta. The function of placentation is to transfer nutrients, respiratory gases, and water from maternal tissue to a growing embryo, and in some instances to remo ...

. 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 fai ...

such as

Lilium ''Lilium'' ( ) is a genus of Herbaceous plant, herbaceous flowering plants growing from bulbs, all with large and often prominent flowers. Lilies are a group of flowering plants which are important in culture and literature in much of the world ...

(see illustration). Septicidal capsules have dehiscence lines aligned with the sutures of the ovary septa or placentae, that is between the carpels. Both loculicidal and septicidal capsules split into distinguishable segments called valves. The valves are a part of the

pericarp 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. Fruitlike structures may develop directly from the seed itself rather th ...

(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 ...

''. 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 annual plant, annuals, biennial plant, biennials, and perennial plant, perennials native plant, native to temperateness, temperate and cold regions of Eurasia, Africa and North America ...

'', the seeds escaping through these pores. Spathoglottis flwrs

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. Orchids are cosmopolitan plants that are found in almost every habitat on Eart ...

willow Willows, also called sallows and osiers, of the genus ''Salix'', comprise around 350 species (plus numerous hybrids) of typically deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions. Most species are known ...

cotton Cotton (), first recorded in ancient India, 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 ...

, 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'', ''Dugandiodendr ...

'', while a

legume Legumes are plants in the pea family Fabaceae (or Leguminosae), or the fruit or seeds of such plants. When used as a dry grain for human consumption, the seeds are also called pulses. Legumes are grown agriculturally, primarily for human consum ...

splits along two sutures, and are a defining feature of the

Fabaceae Fabaceae () or Leguminosae,International Code of Nomen ...

. 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), goober pea, 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 by small and large ...

'' (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 but equally valid) Cruciferae () is a medium-sized and economically important Family (biology), family of flowering plants commonly known as the mustards, the crucifers, or the cabbage family. Most are herbaceous pla ...

, 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 fruits, dry fruit composed of multiple carpels that separate. : Under this definition the mericarps can contain one or more ...

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 huma ...

'' (

Asclepiadoideae The Asclepiadoideae are a subfamily of plants in the family Apocynaceae. Formerly, it was 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, twinin ...

) (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 ...

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 p ...

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 Borago, borage or forget-me-not family, includes about 2,000 species of shrubs, trees, and herbs in 146 to 154 genus, genera with a worldwide distribution. The APG IV system from 2016 classifies the Boraginaceae as single famil ...

and most

Lamiaceae The Lamiaceae ( ) or Labiatae are a family (biology), family of flowering plants commonly known as the mint, deadnettle, or sage family. Many of the plants are aromatic in all parts and include widely used culinary herbs like basil (herb), ba ...

, where the styles are attached between the ovary lobes.

Nuts

Capsules are sometimes mislabeled as

nuts Nut often refers to: * Nut (fruit), fruit composed of a hard shell and a seed * Nut (food), a dry and edible fruit or seed, including but not limited to true nuts * Nut (hardware), fastener used with a bolt Nut, NUT or Nuts may also refer to: A ...

, 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, Europ ...

. 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

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.

References

Bibliography