40. Bulbophyllum nigripetalum Rolfe, Bull. Misc. Inform. Kew. 1891: 197. 1891.
黑瓣石豆兰 hei ban shi dou lan
Rhizome 1.5-3 mm in diam., sections between pseudobulbs 0.6-2.5 cm. Pseudobulbs close, ovoid or broadly conic, 0.9-1.7 × 0.9-1.8 cm. Petiole 0.8-2 cm; leaf blade elliptic, 5.2-17 × 0.6-1.5 cm, obtuse. Inflorescence an elongate, rather lax raceme, erect to spreading, 15-49 cm, 13-32-flowered; peduncle 8-25 cm; bracts ca. 5, longest 4-9 mm; rachis not thickened, 5.5-25 cm, glabrous; floral bracts triangular, 1.8-4.5 × 1-2 mm, acuminate. Flowers spreading to reflexed, secund, not fully opening, many simultaneously, cream-colored or yellow, near base often with blackish purple veins, sometimes blackish purple distally, or blackish purple all over, lip blackish purple, often yellowish at base. Pedicel and ovary 3.8-6.5 mm. Dorsal sepal porrect to recurved, ovate to triangular, 3.1-6 × 1.3-2.2 mm, rather thin, abaxially glabrous, adaxially pubescent, base rather narrowly attached, margin ciliate, apex obtuse to acute; lateral sepals recurved, 3-6 × 2.2-3 mm, otherwise as dorsal sepal. Petals ± porrect, elliptic to obovate or spatulate, 1.6-2.2 × 0.5-1 mm, rather thin with a thick tip, surface pubescent distally, base broadly attached, margins ciliate distally, apex obtuse to acuminate; lip recurved in proximal half, obovate to elliptic, 2.8-4.2 × 1-1.6 mm, thick and fleshy; abaxially with a wide, rounded ridge near base, surface elsewhere convex, partly or entirely velutinous; adaxially somewhat concave near base, with 3 ridges: 2 distinct, obtuse ridges diverging proximally, continuing over 1/3-3/4 of lip, and a thin, low, sometimes inconspicuous median ridge continuing over ca. 1/2 of lip, surface glabrous, finely velutinous toward margins, margins ciliate, apex rounded to obtuse. Column 1-1.3 mm; stelidia triangular, 0.3-0.6 mm, acute. Fl. Mar-May.
Epiphytic or lithophytic in forests; 1000-1300 m. Yunnan [Thailand].