This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", 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..
Gonolobus obliquus var. Shcrtii A. Gray, Syn. Fl. 2:
Stem pubescent, or hirsute with spreading hairs. Leaves downy, broadly ovate, acute or short-acuminate at the apex, deeply cordate at the base and when old with a narrow or closed sinus, 4-7' long, 1 1/2'-5 1/2' wide; petioles stout, pubescent, 1 1/2'- 3' long; peduncles usually longer than the petioles; umbels several-flowered; pedicels 1' long or more; corolla oblong-conic in the bud, dark crimson-purple, its lobes linear, 5"-7" long, 5-7 times as long as the hirsute calyx; crown cup-shaped, fleshy, as high as the anthers, its margin about 10-toothed, the alternate teeth thinner and longer, emarginate or 2-parted, the others broader, thicker, with an obscure internal crest or ridge below the summit; follicles warty.
Gonolobus Baldwinianus Sweet; A. Gray, Syn. Fl. 2:
Part 1, 104. 1876. Vincetoxicum Baldwinianum Britton, Mem. Torr. Club 5: 265. 1894.
Stem pubescent and hirsute. Leaves downy, broadly ovate, acute, or short-acuminate at the apex, deeply cordate at the base, 3'-6' long, or more; petioles hirsute, 1'-2' long; peduncles 6"-12" long, usually longer than the pedicels; umbels several-many-flowered; corolla white or cream-color, the lobes thin, oblong, or becoming spatulate, 4"-5" long; crown thin, the 5 broader lobes quadrate, emarginate, or obscurely toothed; in their sinuses a pair of very slender linear-subulate teeth of more than double their length, much surpassing the stigma.
Missouri and Arkansas to Georgia. May-June.
Periploca graeca L., silk-vine, a handsome woody climber, with glabrous ovate-oblong leaves and brownish flowers in umbels, the obtuse corolla-segments villous on the inner side has been collected as an escape from cultivation.