ASCLEPIADACEAE. 



VOL. III. 



4. GONOLOBUS Michx. Fl. Bor. Am. i: 119. 1803. 

 [AMPELANUS Raf. ; Britton, Bull. Torr. Club 21: 314. 1894.] 



[ENSLENIA Nutt. Gen. i : 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. 



i. Gonolobus laevis Michx. Sand Vine. 

 Enslen's-vine. Fig. 3414. 



Gonolobus laevis Michx. Fl. Bor. Am. i: 119. 1803. 



Enslenia albida Nutt. Gen. i : 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, 

 ii'-5' wide; petioles i'~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. PI. 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 100 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. 



i. 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. i : 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 r -s' long, i' 2i' 

 wide; petioles 2" -12" long; pedicels ii"-3" long; 

 flowers dark purple, about 2i" 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 Vincetoxicum (L.) Pers., with green- 

 ish-white glabrous corollas, another Old World 

 species, is recorded as escaped from cultivation in 

 southern Ontario. 



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