The maple's distinctive fruit are called samaras, and known by many children as "helicopters" by the way they spin as they fall. Inside the fruit are found their seeds, which are in pairs. Each one is enclosed in a "nutlet" attached to a flattened wing of papery tissue. They are shaped to spin as they fall and carry the seeds a considerable distance on the wind. One tree can release hundreds of thousands of seeds at a time. Some seeds can remain in the soil for several years before germinating.