From My Japanese Maple Tree...
Found at Wikipedia:
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 and indehiscent (not opening along a seam). They are winged achenes. The shape of a samara enables the wind to carry the seed farther away from the parent tree:
- The seed can be in the centre of the wing, as in the elms (genus Ulmus) and the hoptree (Ptelea trifoliata).
- The seed can be on one side, with the wing extending to the other side, making the seed autorotate as it falls, as in the maples (genus Acer) and ashes (genus Fraxinus).
Some species that normally produce double samaras, such as Acer pseudoplatanus, can also produce a few multi-lobed samaras with 3 or 4 seeds.