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..
Birthwort Family. Herbs or shrubs, acaulescent, or with erect or twining and leafy stems. Leaves alternate or basal, petioled, mostly cordate or reniform, exstipulate. Flowers axillary or terminal, solitary or clustered, perfect, mostly large, regular or irregular. Calyx-tube (hypanthium) mostly adnate to the ovary, its limb 3-lobed, 6-lobed or irregular. Petals none. Stamens 5-many, inserted on the pistil, the anthers 2-celled, extrorse, their sacs longitudinally dehiscent. Ovary wholly or partly inferior, mostly 6-celled; ovules numerous in each cavity, anatro-pous, horizontal or pendnlons. Fruit a many-seeded mostly 6-celled capsule. Seeds ovoid or oblong, angled or compressed, the testa crustaceous, smooth or wrinkled, usually with a fleshy or dilated raphe; endosperm copious, fleshy.
Six genera and about 200 species, of wide distribution. The family is not closely related to those that precede and follow it in the arrangement followed in this work; its affinity is uncertain.
Acaulescent herbs; perianth regular, 3-lobed, persistent; filaments distinct.
Calyx-tube wholly adnate to the ovary; styles united.
Calyx-tube nearly free from the ovary; styles distinct.
Leafy erect herbs or twining vines; perianth irregular, deciduous; anthers sessile, adnate to the