Convolvulus xanthopotamicus J.R.I.Wood & R.W.Scotland, 2015

Wood, John R. I., Williams, Bethany R. M., Mitchell, Thomas C., Carine, Mark A., Harris, David J. & Scotland, Robert W., 2015, A foundation monograph of Convolvulus L. (Convolvulaceae), PhytoKeys 51, pp. 1-282 : 152-153

133. Convolvulus xanthopotamicus J.R.I.Wood & R.W.Scotland sp. nov. Figures 2c and 17, t. 34-37.

Diagnosis.

Maxime affine Convolvulus ammannii Desr. sed floribus terminalibus solitariis vel in cymis terminalibus dispositis, sepalis corollaque longioribus, caule lignosa distincta.

Type.

CHINA, Shensi, Hancheng Sian, 1914, W. Purdom s.n. (holotype K001067037!; isotypes K!).

Description.

Much branched perennial undershrub with erect stems to c. 20 cm; old stems woody and rigid, weakly divaricate, up to 10 mm thick, new growth herbaceous grey-sericeous. Leaves sessile, 4-40 × 0.5 mm, linear, acute, grey-sericeous. Flowers terminal, solitary or in small dichasial cymes, the branches appressed pilose, up to 6 mm long; bracts and bracteoles not clearly differentiated, 1-10 × 0.5 mm, linear; peduncles not differentiated from the stem; pedicels 1-3 mm; outer se pals 6-7 × 2.5-3.5 mm, elliptic to obovate, caudate, densely pilose; inner sepals 5 × 3-4 mm, ovate, caudate, convex, somewhat scarious, thinly pilose; corolla 1.5-2 cm, unlobed, midpetaline bands pilose; filaments 4 mm long, glabrous, anthers 2 mm, sagittate; ovary 2 mm long, conical, comose, style pilose below, divided 3-7 mm above base, persistent; stigmas 1.75 mm; capsule 2 × 3.5 mm, pubescent, capped by the persistent style; seeds 1.5 × 1 mm, conical with a rounded base, pubescent, blackish-brown.

Distribution.

China: Shanxi, Hanchengsian; Henan, Loyan, Shan Xian, Sanmenxia Gorge, on left bank of Yellow River (M.P. Petrov s.n. [27/5/1957]).

Notes.

Similar to Convolvulus ammannii but flowers all terminal, the stem somewhat woody and slightly divaricate, the sepals and corolla both significantly longer and leaves strictly linear.

This species is only known from two collections from the Hwang Ho (Yellow River) region of north China. The Petrov collection at LE has entirely solitary terminal flowers, while in the Purdom collection (K) some branches terminate in solitary flowers while in others the flowers are arranged in terminal dichasial cymes.

This species may be rare and threatened or simply overlooked but for the time being should be classified as Data Deficient (DD) within IUCN (2012) guidelines. The epithet " xanthopotamicus " refers to the Yellow River or Hwang Ho to whose valley system it is restricted.