Achene
An achene is a dry, one-seeded fruit that does not open at maturity. Its seed is attached to the fruit wall at one point.
Fruit: A mature flowering-plant ovary, sometimes with associated tissues, that contains seeds. Achenes are fruits formed from a single ovary.
Caryopsis: A dry, one-seeded fruit in which the fruit wall is fused to the seed coat. Unlike an achene, a caryopsis has its fruit wall fused to the seed.
Sunflower: A tall flowering plant in the genus Helianthus, cultivated for its seeds and oil. The apparent sunflower seeds are achenes, each enclosing a seed.
Fertilization in flowering plants: The union of a sperm cell and an egg cell in a flowering plant, followed by development of the seed and fruit. Fertilization initiates the development of the seed enclosed by an achene.
Pericarp: The mature ovary wall of a fruit, which surrounds the seed or seeds. In an achene, the pericarp remains distinct from the single seed.
Nut (fruit): A dry, indehiscent fruit with a hard wall, usually containing one seed. A nut is generally larger and has a harder fruit wall than an achene.
Strawberry: An aggregate accessory fruit whose edible flesh develops mainly from the flower’s receptacle. Its small surface achenes are the true fruits, unlike the fleshy receptacle.
Pappus: A tuft or ring of hairs or bristles on certain fruits in the daisy family. On dandelion achenes, the pappus increases drag and enables wind dispersal.
Seed: A plant structure containing an embryo and stored resources, capable of developing into a new plant. An achene contains one seed, attached to its wall at one point.
Samara: A dry, indehiscent fruit with a wing that aids wind dispersal. A samara’s winged fruit wall contrasts with the usually unwinged achene.