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 pinnately veined, alternate, entire or rarely lobed leaves, large solitary flowers, and bitter aromatic bark. Sepals and petals arranged in 3 or more series of 3's, hypogynous, deciduous. Stamens 00; anthers adnate. Carpels 00, separate or coherent, borne on the surface of the elongated receptacle, ripening into an aggregate fruit composed of 1-2-seeded dry or fleshy follicles or achenes. Seeds 1 or 2 in each carpel; endosperm fleshy; embryo very small.
About 10 genera and 75 species, of wide geographic distribution.
Anthers introrse; leaves entire, or with 2 basal lobes; carpels follicular.
Anthers extrorse; leaves lobed or truncate; carpels samaroid.