36 ASCLEPIADACEAE. Vor, IIL. 
4. GONOLOBUS Michx. Fl. Bor. Am. 1: 119. 1803. 
[AmpeLaNnus Raf.; Britton, Bull. Torr. Club 21: 314. 1894.] 
[Enstenia Nutt. Gen. 1: 164. 1818. Not Raf. 1817.] 
Perennial twining herbaceous vines, with petioled opposite cordate thin leaves, and small 
whitish flowers in axillary peduncled clusters. Calyx 5-parted, minutely glandular within, 
the segments lanceolate. Corolla campanulate, deeply 5-cleft, the lobes slightly contorted, 
nearly erect. Crown nearly sessile, of 5 membranous truncate lobes, each appendaged by a 
simple or 2-cleft awn. Stamens inserted at the base of the corolla, the filaments connate 
into a short tube; anthers terminated by an inflexed membrane; pollen-masses solitary in 
each sac, ellipsoid, pendulous. Stigma conic, slightly 2-lobed. Follicles thick, acuminate. 
Seeds comose. [Greek, referring to the somewhat angled pod.] 
Three species, natives of America. Type species: 
Gonolobus laevis Michx. 
1. Gonolobus laévis Michx. Sand Vine. 
Enslen’s-vine. Fig. 3414. 
Gonolobus laevis Michx. Fl. Bor, Am. 1: 119. 1803. 
Enslenia albida Nutt. Gen. 1: 164, 1818, 
A, albidus Britton, Bull. Torr, Club 21: 314. 1894. 
Stem sparingly puberulent, at least above, high- 
climbing, slender. Leaves slender-petioled, ovate, 
gradually acuminate, deeply cordate, palmately 
veined, glabrous or very nearly so, entire, 3’-7’ long, 
13’-s’ wide; petioles 1-4’ long; cymes numerous, 
densely flowered; peduncles stout, 3’-2’ long; flow- 
ers 2-3” long; corolla-segments lanceolate, acute, 
twice as long as those of the calyx and exceeding 
the 2-cleft awns of the corona-lobes; follicles on 
ascending fruiting pedicels, 4’-6’ long, somewhat 
angled, glabrous when mature. 
Along river-banks and in thickets, Pennsylvania to 
Illinois, Kansas, Florida and Texas. June—Aug. 
5. CYNANCHUM L. Sp. Pl. 212. 1753. 
[VINcEToxIcUM Moench, Meth. 717. 1794.] 
Perennial twining herbaceous or slightly woody vines (some species erect herbs), with 
opposite or rarely verticillate or alternate leaves, and small yellowish green or purplish flow- 
ers in axillary cymes. Calyx 5-parted, minutely glandular within. Corolla rotate, deeply 
5-cleft, the segments spreading, somewhat twisted. Crown flat or cup-like, entire, 5-lobed or 
5-parted, the lobes not appendaged. Stamens attached to the base of the corolla, their fila- 
ments connate into a tube; anthers appendaged by an inflexed membrane. Pollen-masses 
solitary in each sac, pendulous. Stigma flat or conic. Follicles acuminate, glabrous. Seeds 
comose. [Greek, dog-strangling.] : 
About too species, natives of both the Old World 
and the New. Besides the following, 2 native species 
occur in the southeastern United States. Type spe- 
cies: Cynanchum acutum L, 
1. Cynanchum nigrum (L.) Pers. Black 
Swallow-wort. Fig. 3415. 
Asclepias nigra L. Sp. Pl. 216, 1753. 
Vincetoxicum nigrum Moench, Meth, 317. 1794. 
Cynanchum nigrum Pers, Syn. 1: 274. 1805. 
Twining, or at first erect, puberulent, slender, 
2°-5° high. Leaves ovate or ovate-lanceolate, en- 
tire, thin, acuminate at the apex, rounded at the 
base, pinnately veined, petioled, 2’-5’ long, 3’-23’ 
wide; petioles 2”-12” long; pedicels 14’-3” long; 
flowers dark purple, about 238” broad; corolla- 
segments pubescent within; crown fleshy, 5-lobed; 
follicles on nearly straight fruiting pedicels, about 
2’ long, glabrous. 
In waste places, escaped from gardens, Massa- 
chusetts to Pennsylvania and Ohio and in British 
Columbia. Introduced from Europe. June—Sept. 
Cynanchum Vincetéxicum (L.) Pers., with green- 
ish-white glabrous corollas, another Old World 
species, is recorded as escaped from cultivation in 
southern Ontario. 
