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..
Perennial climbing vines, with opposite petioled compound leaves, and large showy pe-duncled flowers, solitary in the axils, or at the ends of the branches. Sepals very large, spreading, petaloid, mostly membranous and prominently veined. Petals small, spatulate. Stamens very numerous, the outer ones usually with broadened filaments. Styles long, persistent, plumose. [Ancient Greek name for some vine.]
About 5 species, natives of the north temperate zone. In addition to the following, another occurs in the Rocky Mountains and one in northwestern North America. Type species: Atragene alpina L.
A trailing or partly climbing, somewhat woody, nearly glabrous vine. Leaves trifolio-late; leaflets thin, ovate, acute, toothed or entire, more or less cordate; petioles and petio-lules slender; flowers purplish blue, 2'-4' broad when expanded; sepals 4, thin and translucent, strongly veined, silky along the margins and the veins; petals spatulate, 6"-9" long; persistent styles plumose throughout, about 2' long.
Rocky woodlands and thickets, Hudson Bay to Manitoba, Connecticut, Virginia and Minnesota. Ascends to 3000 ft. in the Catskills. Mountain-or Whorl-leaved-clematis. May-June.