This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Trees or shrubs, with opposite petioled digitately 3-9-foliolate leaves, and conspicuous polygamous irregular flowers in terminal panicles, the bark unpleasantly odorous. Calyx tubular or campanulate, 5-lobed or 5-cleft in the following genus, the lobes unequal. Petals 4-5, unequal, clawed. Disk entire, often I-sided. Stamens 5-8; filaments elongated. Ovary sessile, 3-celled; ovules 2 in each cavity; style slender. Capsule leathery, globose or slightly 3-lobed, smooth or spiny, 3-celled or by abortion 1-2-celled, and often only 1-celled. Seeds large, shining; cotyledons very thick.
The family consists of the following genus, containing about 15 species, of North America and Asia, and Billia, of Mexico, which differs from Aesculus in having distinct sepals.