I liked the following description from the Native Plant Society of Texas (I hope I have the correct tree).

“The fruits are flat, circular and papery wafer-like samaras. They occur in drooping clusters, are retained well into winter and wave in the wind with an audible rattle.”

The samara has a flattened wing of papery tissue that allows the wind to carry the seed. As it turns out, it also allows for nice photos at sunset near the 3/4 mile marker on some walking path. 🙂