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..
Vines or erect perennial herbs, with opposite pinnately compound or simple leaves. Flowers mostly solitary. Sepals 4 or 5, petal-like, valvate in the bud, erect or converging. Petals none. Stamens numerous, parallel with the sepals; anthers narrow, linear. Pistils numerous; styles plumose or silky. Achenes flatfish, the long styles persistent. [Name unexplained.]
About 20 species, natives of Europe and North America, extending into Mexico. In addition to the following, some 10 species inhabit the southern and western parts of North America. Type species: Clematis Viorna L. (Viorna urnigera Spach.). Called Leather-flower or Clematis.
* Climbing vines (no. 2 suberect).
Sepals thin, conspicuously dilated.
Sepals thick, not dilated, their tips recurved.
Leaves, or most of them simple, entire or little lobed; filaments twice as long as the anthers.
Leaves, or some of them, pinnate or trifoliolate.
Fruiting styles silky, not plumose.
Fruiting styles plumose.
Leaves strongly reticulated.
Leaves not strongly reticulated.
Calyx glabrous; anthers short-tipped.
** Erect perennial herbs.
Leaves simple, entire or rarely lobed.
Fruiting styles long, plumose; eastern species.
Flowers yellowish-green; achenes straight.
Flowers purple; achenes distinctly oblique.
Fruiting styles short, silky; western species.
Leaves pinnate, or the lowest entire.
Clematis crispa L. Sp. Pl. 543. 1753.
Clematis cylindrica Sims, Bot. Mag. pl. 1160. 1809.
Viorna cylindrica Spach, Hist. Veg. 7: 269. 1839- Viorna crispa Small, Fl. SE. U. S. 437. 1903.
A climbing vine. Leaves pinnate; leaflets mostly trifoliolate, the ultimate divisions entire or occasionally lobed, glabrous and thin; flowers solitary, nodding, bluish-purple, 9"-18" long; calyx cylindric below, but the sepals thin and widely spreading above, their margins undulate; filaments hairy; persistent styles silky, not plumose.