botany Botany, also called plant science (or plant sciences), 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 "bot ...

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 partic ...

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. They include all forbs (flowering plants without a woody stem), grasses and grass-like plants, a vast majority of ...

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 ...

: ''capsula'', small box) is derived from a compound (multicarpeled) ovary. A capsule is a structure composed of two or more carpels. In (flowering plants), the term locule (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 (; ) 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) '' pistil ...

may be equal to or less than the number of carpels. The locules contain the ovules 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 angiosper ...

s and are separated by septa.

Dehiscence

In most cases the capsule is dehiscent, i.e. at maturity, it splits apart (dehisces) to release the

s within. A few capsules are indehiscent, for example those of '' Adansonia digitata'', '' Alphitonia'', and ''

Merciera ''Merciera'' is a genus of plants in the family Campanulaceae. It contains 6 known species, all endemic to Cape Province in South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. I ...

''. 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, ''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 refers to the formation, type and structure, or 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 remove ...

. This type is common among many members of the Liliaceae such as Lilium (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 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''. 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'', the seeds escaping through these pores. Spathoglottis flwrs

Examples of other plants that produce capsules include nigella, orchid, willow,

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 p ...

, and

jimson weed ''Datura stramonium'', known by the common names thorn apple, jimsonweed (jimson weed), devil's snare, or devil's trumpet, is a poisonous flowering plant of the nightshade family Solanaceae. It is a species belonging to the '' Datura'' genus ...

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'', 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'' (peanuts). Capsules derived from two carpels include

silicles A silique or siliqua (plural ''siliques'' or ''siliquae'') is a type of fruit (seed capsule) having two fused carpels with the length being more than three times the width. When the length is less than three times the width of the dried fruit ...

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, silicles have a ratio of length to width of no more than 3:1. A schizocarp 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'' ( Asclepiadoideae) (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 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 and most Lamiaceae, 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, or a collective noun for dry and edible fruits or seeds * Nut (hardware), fastener used with a bolt Nut or Nuts may also refer to: Arts, entertainment, and media Com ...

, as in the example of the Brazil nut or the Horse-chestnut. 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.

References

Bibliography