ASCLEPIADACEAE. 747 



within, the segments lanceolate. Corolla campanulate, deeply 5-cleft, the lobes 

 slightly contorted, nearly erect. Crown nearly sessile, of 5 membranous truncate 

 lobes, each apperidaged 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, angled, acuminate. [Greek, 

 angle-pod.] Two species, natives ot America. 



i. Gonolobus laevis Michx. SAND VINE. (I. F. f. 2929.) Stem sparingly 

 puberulent, at least above, high -climbing, slender. Leaves ova Je, gradually acu- 

 minate, palmately veined, glabrous or very nearly so, entire, 8-18 cm. long; cymes 

 usually numerous, rather densely flowered; peduncles stout, 6 mm. -5 cm. long; 

 flowers 4-6 mm. 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, 10-15 cm - l n g> glabrous when 

 mature. Along river-banks and in thickets, Penn. to 111., Kans., Fla. and Tex. 

 June- Aug. \Ampelanus albidus (Nutt.) Britton.] 



5. CYNANCHUM L. [VINCETOXICUM Moench.] 



Perennial vines (some species erect herbs), with opposite or rarely verticillate 

 or alternate leaves, and small yellowish green or purplish flowers in axillary cymes. 

 Calyx 5-parted, minutely glandular within. Corolla rotate, deeply 5 cleft, the seg- 

 ments 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. Pollen- 

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

 glabrous. [Greek, dog-strangling, alluding to its poisonous qualities.] About 100 

 species, natives of warm and temperate regions. Besides the following, 2 native 

 species occur in the southeastern U. S. 



i. Cynanchum nigrum (L.) Pers. BLACK SWALLOW-WORT. (I. F. f. 2930. ) 

 Twining, or at first erect, stem slightly puberulent, slender, 6-15 dm. high. 

 Leaves ovate or ovate-lanceolate, entire, thin, acuminate at the apex, rounded at 

 the base, pinnately veined, petioled, 5-13 cm. long, glabrous, or puberulent beneath; 

 petioles 4-25 rnm. long; flowers purple, 5 mm. broad; crown fleshy, 5-lobed; follicles 

 on nearly straight fruiting pedicels, about 4 mm. long, glabrous. Waste places, 

 escaped from gardens, Mass, to Penn. and Ohio. Introduced from Europe. 

 June-Sept. 



6. VINCETOXICUM Walt. 



Perennial vines, with opposite usually cordate leaves, and rather large flowers 

 in axillary umbel-like cymes or fascicles. Calyx 5-parted or deeply 5-cleft, mostly 

 5 glandular within. Corolla rotate, very deeply 5-parted, the tube very short, the 

 segments convolute in the bud. Corona (crown) annular or cup-shaped, adnate to 

 the corolla. Stamens inserted on the base of the corolla, the filaments connate into a 

 tube; anthers not appendaged, merely tipped, borne along or just under the margin 

 of the flat-topped stigma, the sacs more or less transversely dehiscent. Pollen- 

 masses solitary in each sac, horizontal or nearly so. Follicles thick, acuminate, 

 smooth, angled or tuberculate. [Greek, subduing poison.] About 75 species, natives 

 of America. Besides the following, some 10 others occur in the southern U. S. 

 Crown annular, lo-crenate; folicles angled, not warty. 



Corolla about twice as long as the calyx. i. V. suberosum. 



Corolla 3-4 times as long as the calyx. 2. /'. gonocarpos* 



Crown cup-shaped, about as high as the anthers; follicles warty. 

 Flowers purple to dull yellow. 



Corolla-segments oblong, 6-9 mm. long. 3. V. htrsutum. 



Corolla-segments linear or linear-oblong, 11-15 mm. long. 



Crown merely crenulate. 4. V* obttquum* 



Crown toothed or lobed. 



Crown 5-lobed, with a subulate 2-cleft tooth in each sinus. 



5. V. Carolinen \ 

 Crown lo-toothed, the alternate teeth thinner and longer. 



6. V. Shortii. 

 Flowers white. 7. V. Baldwintanum. 



