ABSTRACT. Cynanchum wangii, a new species from Yunnan, China, is described, and a photograph of the type specimen is given.

Cynanchum is a genus of about 200 species, of which 53 species and 12 varieties were recognized in China by Tsiang & Li (1977). With the addition of five other species by P. T. Li (1983, 1990) and C. wangii, the total number of species of Cynanchum in China is now 59. The genus is difficult taxonomically, and D. Z. Li (1990) and Qiu (1989) have treated it as several segregate genera. However, most Chinese taxonomists (e.g., Tsiang & Li, 1977; P. T. Li, 1991) agree that the larger concept represents a natural genus.

Cynanchum wangii P. T. Li & W. Kittredge, sp. nov. TYPE: China. Yunnan: Meng-Nun, Jenn-Yeh Hsien, 750 m, riverbank, Nov. 1936, C. W. Wang 80897 (holotype, A; isotypes, IBSC, KUN, PE). Figure 1.

Herba perennis erecta 10--20 cm alta; caule ramoso puberulo. Folia linearia glabra, 5--20 X 1--2 mm. Cymae 3--7-florae, extra-axillares vel terminales; pedunculis gracilibus 3--8 cm longis, puberulis. Flores calyx intus as bases sinuum 5-glandulifero, lobis ovato-triangularibus, glabris, ca. 0.5 X 0.5 mm; corolla viridi-flava, rotata, extus glabra, intus dense pubescente; corona applanata ad dorsum gynostegii adnata gynostemio breviore 5-partita, lobis semiorbiculatis, ca. 0.5 X 0.5 mm; staminibus stigma aequantibus, antheris oblongis membranaceis, connectivis orbiculatis, polliniis longe ovoideis, pendulis, retinaculo oblongo, caudicula brevissima; ovariis glabris, stigmate basi discoideo-pentagono; ovulis numerosis.

Erect perennial herbs 10--20 cm tall; stem many-branched, ca. 1 mm diam.; uniformly puberulous, internodes 0.8--3.5 cm long; branchlets delicate, puberulous. Leaves opposite, linear, 5--20 X 1--2 mm, glabrous, base cuneate, apex rounded or obtuse; midrib flat on both surfaces, lateral veins obscure. Cymes umbelliform or corymbose, 3- to 7-flowered, extra-axillary or terminal, solitary; peduncles delicate, 3--8 cm long, puberulous; pedicels 4--7 mm long. Calyx with 5 basal glands inside, calyx lobes ovate-triangular, 0.5 X 0.5 mm, glabrous; corolla greenish yellow, rotate, membranous, tube ca. 1 mm, glabrous, lobes oblong-lanceolate, ca. 4 mm long, 1 mm wide, glabrous outside, densely pubescent inside; outer corona absent, inner one inserted at base of gynostegium, 5-partite, lobes semiorbicular, 0.5 X 0.5 mm, erect, somewhat fleshy, apex rounded, nearly half as long as anther membrane; anthers oblong, apical membrane rounded, as high as stigma; pollinia oblong-ovoid, pendulous, retinaculum oblong, caudicle very short; ovaries long-ovoid, glabrous; stigma pentagonal-disklike; apex slightly elevated; ovules numerous in each carpel.

Flowering May through August, fruiting October through November; grows along riverbanks at altitudes of ca. 700--900 m.

Paratypes. [smChina. yunnan[nm: Mong-Hain, Gan-Lan-Ba, Ching-Hung Hsien, Wang 79920 (A); Lann-Tsang Hsien, Wang 76710 (A).

Cynanchum wangii, which is so far only known from three collections, is most closely related to C. stenophyllum Hemsley, a species distributed in Hubei and Guizhou provinces, China. It is readily distinguished from the latter by its small, slender leaves 1--2 mm wide, umbellate or corymbose inflorescences longer than leaves, greenish yellow flowers, oblong-lanceolate corolla lobes, and 5-partite corona nearly half as long as the anther membrane.

Acknowledgments. We are grateful to David E. Boufford, Bryan Dutton, and Ihsan Al-Shehbaz for help with the manuscript. Thanks also to Roy Gereau for checking the Latin.

Literature Cited

Li, D. Z. 1990. The chemotaxonomy of Cynanchum and its allied genera. Acta Phytotax. Sin. 28: 461--470.

Li, P. T. 1983. Three new species of Asclepiadaceae from China. Bull. Bot. Res. 3: 103--109.

Li, P. T. 1990. New materials of Asclepiadaceae from Chinese Hengduanshan Region. Acta Bot. Yunnan. 12: 19--21.

Li, P. T. 1991. A new genus of Euphorbiaceae and some new nomenclatural combinations of the Asclepiadaceae plants. J. South China Agr. Univ. 12(3): 38--42.

Qiu, S. X. 1989. Chemotaxonomy of Cynanchum and its allied genera, with notes on the generic characteristics of Vincetoxicum. Acta Bot. Yunnan. 11: 41--50.

Tsiang, Y. & P. T. Li. 1977. Cynanchum. Flora Reipublicae Popularis Sinicae 63: 309--384.