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..
Herbs, shrubs, vines or some tropical genera trees, with opposite or verticillate simple stipulate leaves, or the leaf-bases connected by a stipular line or membrane, and regular perfect 4-5-parted mostly cymose or spicate flowers. Calyx inferior, the tube campanulate, sometimes short or none, the segments imbricated, at least in the bud. Corolla gamopetalous, funnelform, campanulate, or rarely rotate. Stamens as many as the lobes of the corolla, alternate with them, inserted on the tube or throat; anthers 2-celled, the sacs longitudinally dehiscent; pollen-grains simple. Disk usually none. Ovary superior, 2-celled (rarely 3-5-celled); style simple, 2-5-cleft or 2-divided, rarely 4-cleft; ovules numerous or few in each cavity, anatropous or amphitropous. Fruit a 2-valved capsule in our species. Seeds winged or wingless; embryo small, usually straight; endosperm copious; cotyledons narrow or foliaceous; radicle terete or conic.
About 30 genera and 400 species, widely distributed in warm and tropical regions.
Style 4-cleft; woody vine; flowers large, yellow.
Style simple, 2-lobed or 2-divided with a common stigma; herbs.
Corolla-lobes valvate; capsule didymous or 2-lobed; leaves broad.
Style simple, jointed; spike simple.
Style 2-divided below; spikes cymose.
Corolla-lobes imbricate; capsule subglobose; leaves linear.