i6 



ASCLEPIADACEAE. 



[Vol. III. 



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

 [Ensi.knia Nutt. Gen. i; 164. 1S18. Not Raf. 1S17.] 



Perennial twining herbaceous vines, with petioled opposite cordate thin leaves, and small 

 whitish flowers in axillary peduncled cymes. 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 appeudaged 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 coniose. [Greek, vine-like.] 



Three species, natives of .\merica. 



I. Ampelanus albidus CNutt.) Britton. 

 Sand \'ine. (Fig. 2929.) 



Enslenia alhida Nutt. Gen. i: 164. 181S. 

 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 verj' nearly so, entire, 3'-7' 

 long, 1%'-$' wide; petioles i'-4' long; cymes 

 usually numerous, rather densely flowered; pe- 

 duncles stout, 3"-2' long; flowers 2"-3" long; 

 corolla-segments lanceolate, acute, about twice as 

 long as those of the calyx and slightly exceeding 

 the 2 cleft awns of the corona-lobes; follicles 

 erect on the ascending fruiting pedicels, 4'-6' 

 long, glabrous when mature. 



Along; river-banks and in thickets, southern Penn- 

 sylvania to Illinois and Kansas, south to Florida and 

 Texas. ]une-.\ug. 



5. CYNANCHUM L. Sp. PI. 212. 1753. 



[ViNXEToxicuM IMoench, Meth. 717. 1794. Not Walt. 17S8.] 

 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 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. PoUen-masses 

 solitary in each sac, pendulous. Stigma flat or conic. Follicles acuminate, glabrous. 

 Seeds comose. [Greek, dog-strangling, alluding to its poisonous qualities.] 



About 100 species, natives of warm and temperate 

 regions of both tlie Old World and the Xew. Be- 

 sides the following:, 2 native species occur in the 

 southeastern United States. 



I. Cynanchum nigrum (L.) Pers. 

 Black Swallow-wort. (Fig. 2930.) 



Asclepias nigra L. Sp. PI. 216. I75,v 

 Vincclo.vicum nigitnn Moench, Jleth. 317. 1794. 

 Cyianclium nigrum Pers. Sjm. i: 274. 1S05. 



Twining, or at first erect, stem slightly puber- 

 ulent, slender, 2°-5° high. Leaves ovate or 

 ovate-lanceolate, entire, thin, acuminate at the 

 apex, rounded at the base, pinnately veined, 

 petioled, 2'-5' long, j4'-2/j' wide, glabrous, or 

 puberulent beneath; petioles 2"-i2" long; ped- 

 icels i/-2"-3" long; flowers dark purple, about 

 2^2" broad; crown flesh}-, 5-lobed; follicles on 

 nearly straight fruiting pedicels, about 2' long, 

 glabrous. 



In waste places, escaped from gardens, Massa- 

 chusetts to Pennsylvania and Ohio. Introduced 

 from Europe. June-Sept. 



