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..
Ascending or suberect, 1°-3° long, simple or branched, tufted, glaucous and glabrous. Lower leaves simple, entire or 1-4-lobed, obtuse, deep bluish-green above, glaucous beneath, sessile, clasping, 2'-4' long; upper leaves pinnate, or sometimes simple, tendril-bearing; leaflets 2-4, ovate, sessile; flowers solitary, terminal and axillary, purplish, nodding; calyx ovoid, 9"-15" long, 5"-7" broad, contracted near the summit; sepals thick, lanceolate, acute, their tips recurved; stamens numerous, pubescent above, filaments twice as long as the anthers; achenes flat, nearly orbicular, silky-pubescent; persistent styles 1'-1 1/4' long, brownish-plumose throughout.
Clematis viornioides Britton is a hybrid between this and V. Viorna. Roanoke, Va.
Clematis Pitcheri T. & G. Fl. N. A. 1: 10. 1838. V. Simsii Small, Fl. SE. U. S. 438. 1903. Not Clematis Simsii Sweet.
A high climbing vine, the branches more or less pubescent. Leaves pinnate; leaflets entire, lobed or trifoliolate, thick, reticulated, generally mucronate; flowers solitary; calyx campanu-late, less than 1' long, purplish, pubescent; sepals with recurved margined tips; filaments hairy; persistent styles more or less pubescent, about 1' long.
Clematis versicolor Small; Britton, Man. 421. 1901.
Viorna versicolor Small, Fl. SE. U. S. 438. 1903.
A branching vine, up to 12° long, glabrous or slightly pubescent below the nodes. Leaves pinnate, slender-petioled; leaflets firm, apiculate, oblong to ovate-lanceolate, ¥-3' long, conspicuously reticulate, very glaucous beneath; sepals thin, purplish, lanceolate, about 10" long, glabrous, slightly recurved at the tip, achenes pubescent; persistent styles plumose, white or nearly so.
Rocky ledges, Missouri and Arkansas. July.
Clematis Viorna L. Sp. Pl. 543. 1753.
Viorna Viorna Small, Fl. SE. U. S. 439. 1903.
A vine, climbing to the height of 10° or more over bushes in rich soil. Leaves mostly pinnate; leaflets glabrous, entire, lobed or trifoliolate; uppermost and lowest leaves often entire; calyx ovoid-campanulate, purple, the sepals remarkably thick; filaments about as long as the anthers; persistent styles plumose throughout, 1' long or more, brownish.
Banks and thickets, southern Pennsylvania to West Virginia, Georgia and Indiana. Ascends to 4000 ft. in Virginia. May-July.
Viorna fláccida Small, differing by entire, more pubescent leaflets, the calyx lavender with green tips, occurs in Kentucky and Tennessee.
Viorna Ridgwayi Standley, of Illinois, has long-tipped leaf-lobes or leaf-segments.