A samara is a type of fruit in which a flattened "wing" of fibrous, papery tissue develops from the ovary wall. A samara is a simple dry fruit that is bicarpellate (formed from two carpels) and indehiscent (not opening along a seam). The shape of a samara enables the wind to carry the seed away from the parent tree. A particular form of samara is sometimes called a key, where the papery sheath extends far out to one side so that the seed spirals as it falls. Trees with rounded samaras include the elms (genus Ulmus) and the hoptree (Ptelea trifoliata). Trees with the elongated keys include the maples (genus Acer) and the ashes (genus Fraxinus).
