Utricle

Small, bladderlike, thin-walled, one-seeded, indehiscent fruit. Although it is seldom seen by casual observers, this is the characteristic fruit of the duckweed family (Lemnaceae). The dehiscent one-seeded fruits of Amaranthus (Amaranthaceae) are often called circumscissile utricles because the top half of the fruit separates, exposing a shiny black seed.