Samara (fruit)
A samara is a winged achene, 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, and is indehiscent. The shape of a samara enables the wind to carry the seed further away from the tree than regular seeds would go, and is thus a form of anemochory.
In some cases the seed is in the centre of the wing, as in the elms, the hoptree, and the bushwillows. In other cases the seed is on one side, with the wing extending to the other side, making the seed autorotate as it falls, as in the maples and ash trees.
There are also single-wing samara such as mahogany which have a shape that enables fluttering.
Some species that normally produce paired samaras, such as Acer pseudoplatanus, can also produce them in groups of three or four.