i8 



ASCLEPIADACEAE. 



[Vol.. III. 



Vincetoxicum gonocarpos laevis (Michx.) Britton, Mem. Torr. Bot. Club, 5: 266. 1894. 

 Gonolobus laevis Michx. Fl. Bor. Am. 1: 119. 1803. 



Usually glabrous; sinus of the leaves open. Near Washington, D. C, Kansas (according to B. 

 B. Sm3'th), south to Mississippi and Texas. 



3. Vincetoxicum hirsutum (Michx.) Brit- 

 ton. Hairy Vincetoxicum. (Fig. 2933.) 



Gonolobus hirsutus Michx. Fl. Bor. Am. 1: 119. 1803. 

 V. hirsutum Britton, Mem. Torr. Club, 5: 266. 1894. 



Stem downy, slender. Leaves ovate, acuminate 

 at the apex, deeply cordate at the base, downy, i f -\ r 

 long, i / -2 Vz r wide, the sinus narrow, or the lobes 

 sometimes overlapping; petioles slender, pubescent, 

 % f -2. f long; peduncles usually about equalling the 

 petioles, sometimes longer; umbels few-several- 

 flowered; corolla brown-purple to greenish yellow, 

 ovoid in the bud, its segments oblong, very obtuse, 

 3 // ~4 // long, minutely puberulent without, about 4 

 times as long as the densely pubescent calyx; crown 

 cup-shaped, fleshy, about as high as the anthers, 

 the margin 10-crenate; follicles lanceolate, 3 / -5 / 

 long, muricate, puberulent; seeds entire. 



In thickets, Maryland to Florida, west to Tennessee. 

 July-Aug. 



4. Vincetoxicum obliquum (Jacq.) Britton 



(Fig. 2934.) 



Cynanchum hirtum L. Sp. PI. 212. 1753? 

 Cynanchum obliquum Jacq. Coll. 1: 148. 1786. 

 G. obliquus R. Br.; R. & S. Syst. 4: 64. 1820. 

 V. obliquum Britton, Mem. Torr. Club, 5: 266. 1894. 



Stem puberulent or hirsute, slender. Leaves 

 pubescent, broadly ovate, acuminate at the apex, 

 deeply cordate at the base with an open or 

 closed sinus, 2 / -8 / long, i^ / -6 / wide; petioles 

 rather stout, pubescent, \ f -/\? long; umbels slen- 

 der-peduncled, few-flowered; pedicels very slen- 

 der, i/-2 / long; corolla narrowly conic in the 

 bud, red-purple within, greenish and minutely 

 pubescent without, its segments elongated-lin- 

 ear, obtuse, 6-7 times as long as the hirsute 

 calyx; crown cup-shaped, as high as the an- 

 thers, fleshy, its margin 10-crenulate, the inter- 

 mediate crenulations sometimes 2-dentate; fol- 

 licles ovoid-lanceolate, 2 / -3 / long, muricate. 



In thickets, Pennsylvania to Ohio, south to Vir- 

 ginia and Kentucky. July-Aug. 



Large-flowered Vincetoxicum. 



5. Vincetoxicum Carolinense (Jacq.) Brit- 

 ton. Carolina Vincetoxicum. (Fig. 2935.) 



Cynanchum Carolinense Jacq. Coll. 2: 228. 1788. 

 G. Caroiinensis R. Br.; R. & S. Syst. 6: 62. 1820. 

 V. Carolinense Britton, Mem. Torr. Club, 5: 265. 1894. 



Stem hirsute. Leaves broadly ovate, acute or 

 short-acuminate at the apex, deeply cordate at the 

 base with a narrow or closed sinus, 3 / -7 / long, 

 2 / -5)^ / wide, pubescent, at least beneath; petioles 

 hirsute, i^ / -4 / long; peduncles 2 / -4 / long; pedicels 

 very slender, i / long or more; corolla brown-pur- 

 ple, oblong-conic in the bud, puberulent without, 

 its segments linear-oblong or linear-lanceolate, ob- 

 tusish, 5 // -6 // long, 5-6 times longer than the hir- 

 sute calyx; crown cup-shaped, scarcely fleshy, 5- 

 lobed, with a subulate longer 2-cleft erect tooth in 

 each sinus; follicles muricate. 



In thickets, Virginia to Missouri, south to South 

 Carolina and Louisiana. May-July. 



