Samara (fruit)

A samara is a form of tree seed in which the seed is somewhat flattened and encased within a flat sheath of fibrous, papery tissue. This form enables the wind to carry the seed a short distance away from the parent tree. A particular form of samara is sometimes called a key, where the paper sheat extends far out to one side so that the seed spirals as it falls, helping it to move out from the parent tree. 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).