horse chestnut, common name for some members of the Hippocastanaceae, a family of trees and shrubs of the north temperate zones and of South America. The horse chestnut tree, Aesculus hippocastanum, a native of the Balkan peninsula, is now cultivated in many countries for shade and ornament. Buckeyes are several similar but often smaller North American species of the same genus. Horse chestnuts and buckeyes (as the nuts too are called) somewhat resemble true chestnuts in appearance but are edible only after careful preparation. Some Native Americans ate buckeyes in large quantity after thorough roasting or leaching. Buckeyes, with their eyelike markings, are still carried as charms by some rural people. Ohio is called the Buckeye State from the prevalence of the Ohio buckeye, A. glabra. The wood of the horse chestnut and of the buckeye is soft; it has been used for paper pulp and for carpentry, woodenware, and other similar purposes. A compound derived from the buckeye, aesculin, is a pharmaceutical used as an anti-inflammatory. The only other genus of the family is Billia, evergreens ranging from Colombia to Mexico. Horse chestnuts are classified in the division Magnoliophyta, class Magnoliopsida, order Sapindales, family Hippocastanallae.