What is "buttonball"

Plane \Plane\, n. [F., fr. L. platanus, Gr. ?, fr. ? broad; -- so called on account of its broad leaves and spreading form. See Place, and cf. Platane, Plantain the tree.] (Bot.) Any tree of the genus Platanus.

Note: The Oriental plane ( Platanus orientalis) is a native of Asia. It rises with a straight, smooth, branching stem to a great height, with palmated leaves, and long pendulous peduncles, sustaining several heads of small close-sitting flowers. The seeds are downy, and collected into round, rough, hard balls. The Occidental plane ( Platanus occidentalis), which grows to a great height, is a native of North America, where it is popularly called sycamore, buttonwood, and buttonball, names also applied to the California species ( Platanus racemosa).

n. A tree, the buttonwood.