This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", 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 with alternate pinnately compound leaves, and monoecious bracteolate flowers, the staminate in long drooping aments; the pistillate solitary or several together. Staminate flowers consisting of 3-numerous stamens with or without an irregularly lobed perianth adnate to the bractlet, very rarely with a rudimentary ovary. Anthers erect, 2-celled, the sacs longitudinally dehiscent; filaments short. Pistillate flowers bracted and usually 2-bracteolate, with a 3-5-lobed (normally 4-lobed) calyx or with both calyx and petals, and an inferior 1-celled or incompletely 2-4-celled ovary. Ovule solitary, erect, orthotropous; styles 2, stigmatic on the inner surface. Fruit in our genera a drupe with indehiscent or dehiscent, fibrous or woody exocarp (husk; ripened calyx; also regarded as an involucre), large, 2-4-lobed. Endosperm none. Cotyledons corrugated, very oily. Radicle enclosing the bony endocarp or nut which is incompletely 2-4-celled. Seed minute, superior.
Six genera and about 35 species, mostly of the warmer parts of the north temperate zone, extending in America south along the Andes to Bolivia. The young leaves in the bud are stipulate in at least two species of Hicoria. The family is not closely related to the other ament-bearing ones; its affinity is with the Anacardiaceae.
Husk indehiscent; nut rugose.
Husk at length splitting into segments; nut smooth or angled.