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 or shrubs, with alternate or basal (rarely opposite) simple entire lobed or laciniate stipulate leaves, and solitary or clustered flowers. Sepals 5, equal or unequal. Flowers perfect, mostly irregular. Petals 5, hypogynous, imbricated in the bud, the lower one generally larger or spurred. Perfect stamens 5, hypogynous; anthers erect, connivent in a ring, or syngenesious, sessile or on short filaments. Ovary 1, 1-celled; placentae 3, parietal; style simple; stigma generally oblique. Capsule dehiscent by valves (except in some tropical genera with berrylike fruit). Seeds anatropous, with a crustaceous testa; embryo mainly straight, in copious endosperm.
About IS erenera and 300 species. of wide distribution.
Sepals more or less prolonged posteriorly.
Sepals not prolonged posteriorly.
Petals nearly equal; stamens syngenesious.
Petals very unequal; anthers only connivent.