2. Desmodium diffusum Candolle, Ann. Sci. Nat. (Paris). 4: 100. 1825.
单序山蚂蝗 dan xu shan ma huang
Desmodium laxiflorum Candolle var. formosense Ohwi; D. laxiflorum subsp. parvifolium H. Ohashi & T. T. Chen; D. unibotryosum C. Chen & X. J. Cui; Hedysarum diffusum (Candolle) Roxburgh (1832), not Willdenow (1801).
Subshrubs or shrubs, nearly erect, 30-100 cm tall. Branchlets with adpressed and minute hooked hairs. Leaves 3-foliolate; petiole 1-4 cm; terminal leaflet blade rhombic-ovate or obovate, shorter than 9 cm, abaxially densely yellow sericeous, adaxially sparsely adpressed hairy, lateral veins 7-9, apex acute. Racemes solitary, often terminal, to 25 cm; rachis pubescent intermixed with minute hooked hairs. Pedicel 3-5 mm, densely hairy as rachis. Calyx densely villous; upper lobes minutely 2-toothed at apex. Corolla white to violet, 4-7 mm; standard broadly obovate or orbicular. Legume linear, 2-6 cm, with dense, minute, hooked hairs, 4-12-jointed, both sutures distinctly constricted between articles; articles oblong. Fl. and fr. Aug-Nov.
Thickets, forest margins, mountain slopes; 100-2500 m. Guangdong, Guangxi, Taiwan, Yunnan [India, Indonesia, Laos, Myanmar, Nepal, Philippines, Thailand, Vietnam].
This species has been confused with Desmodium laxiflorum. However, it is well distinguished from it by terminal leaflets rhombic-ovate or obovate, shorter than 9 cm, acute at apex, lateral veins often 7-9 pairs; racemes solitary; pedicel 3-5 mm; upper calyx lobe 2-toothed at apex; and both sutures of legume distinctly constricted between articles.