This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", 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, shrubs or woody vines, a few exotic species herbs, with opposite (rarely alternate) compound or simple leaves, and mostly large and showy, clustered terminal or axillary, more or less irregular flowers. Calyx inferior, gamosepalous. Corolla gamopetalous, funnelform, campanulate, or tubular, 5-lobed, somewhat 2-lipped, at least in the bud. Anther-bearing stamens 2 or 4, inserted on the tube of the corolla and alternate with its lobes; anthers 2-celled, the sacs longitudinally dehiscent. Disk annular or cup-like. Ovary sessile or stalked, mostly 2-celled; placentae parietal, or on the partition-wall of the ovary; ovules very numerous, horizontal, anatropous; style slender; stigma terminal, 2-lobed. Capsule 2-valved, loculicidally, septifragally or septicidally dehiscent. Seeds flat, transverse, winged in our genera; endosperm none; cotyledons broad and flat, emarginate or 2-lobed; radicle short, straight.
About 60 genera and over 500 species of wide geographic distribution in tropical regions, a few in the north and south temperate zones. Leaves compound; anther-bearing stamens 4; our species vines.
Calyx-limb undulate; capsule flattened parallel with its partition-wall.
Calyx 5-toothed; capsule compressed at right angles to its partition-wall.
Leaves simple; anther-bearing stamens mostly 2; trees.