Anachene (/əˈkiːn/;[1] from Ancient Greek ἀ (a) 'privative' and χαίνειν (khaínein) 'to gape'),[2] also sometimes calledakene and occasionallyachenium orachenocarp, is a type ofsimpledryfruit produced by many species offlowering plants. Achenes are monocarpellate (formed from onecarpel) andindehiscent (they do not open at maturity). Achenes contain a singleseed that nearly fills thepericarp, but does not adhere to it. In many species, what is called the "seed" is an achene, a fruit containing the seed. The seed-like appearance is owed to the hardening of the fruit wall (pericarp), which encloses the solitary seed so closely as to seem like a seed coat.[2]
The fruits ofbuttercup,buckwheat,caraway,quinoa,amaranth, andcannabis are typical achenes.
The achenes of thestrawberry are sometimes mistaken for seeds. The strawberry is anaccessory fruit with an aggregate of achenes on its outer surface, and what is eaten is accessory tissue.
Arose produces an aggregate of achene fruits that are encompassed within an expandedhypanthium (aka floral tube), which is a structure where basal portions of the calyx, the corolla, and the stamens unite with the receptacle to form a cup-shaped tube.
A winged achene, as inmaple, is called asamara.
Some achenes have accessory hair-like structures that cause them to tumble in the wind in a manner similar to atumbleweed. This type sometimes is called a tumble fruit ordiaspore. An example isAnemone virginiana.
Acaryopsis orgrain is a type of fruit that closely resembles an achene, but differs in that the pericarp is fused to the thin seed coat in the grain.
Anutricle is like an achene, but the fruit is bladder-like or inflated.[3]
Fruits ofsedges are sometimes considered achenes although their one-locule ovary is a compoundovary.
The fruit of the familyAsteraceae is also so similar to an achene that it is often considered to be one, although it derives from a compound inferior ovary (with onelocule). A special term for the Asteraceae fruit is cypsela (plural cypselae or cypselas). For example, the white-gray husks of asunflower "seed" are the walls of the cypsela fruit.[clarification needed] Many cypselas (e.g.dandelion) have modifiedcalyx tissue calledpappi attached that functions inbiological dispersal of the seed.
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