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..
Shrubs or trees or vines with simple opposite leaves and no stipules. Flowers perfect or the exterior ones of the clusters sterile and conspicuous. Petals and sepals generally 5. Stamens twice as many as the sepals, or numerous, epigynous. Carpels 2-10, wholly united or the apex free, the lower half at least enclosed by and adnate to the calyx. Seeds numerous; endosperm generally copious; embryo small.
About 16 genera and 80 species, of temperate and tropical regions.
Sepals and petals 5 or fewer; shrubs.
Petals valvate; stamens 8 or 10; corolla small.
Petals convolute; stamens 15-60; corolla large.
Sepals and petals 7 or more; woody vine.