31. Euphorbia royleana Boissier in A. Candolle, Prodr. 15(2): 83. 1862.
霸王鞭 ba wang bian
Euphorbia pentagona Royle, Ill. Bot. Himal. Mts. 329. 1836, not Haworth (1828).
Small trees or shrubs, 5-7 m tall, glabrous except for cyathia. Stems 4-7 cm thick, green, 5-7-angled, many branching from upper parts; ribs with rounded teeth/tubercles. Leaves alternate, apically clustered; stipules pricklelike, spines paired, 3-5 mm; petiole absent; leaf blade oblanceolate to spoon- shaped, 5-15 × 1-4 cm, slightly succulent, base attenuate, margin entire, apex obtuse or subtruncate; veins inconspicuous. Cyathia in subterminal cymes, yellow, peduncle ca. 5 mm; cyathophylls as long as involucre, membranous; involucre ca. 2.5 × 2.5 mm; glands 5, transversely elliptic, dark yellow. Capsule 3-lobed, 1-1.2 × 1-1.5 cm, smooth and glabrous. Seeds 3-3.5 × 2.5-3 mm, brown, adaxially striate; caruncle absent. Fl. and fr. May-Jul.
Subtropical rainshadow valleys, forming its own communities on rocky slopes. W Guangxi, S Sichuan, Taiwan, Yunnan [Bhutan, N and NE India, Myanmar, Nepal, Pakistan].
Euphorbia royleana is grown as a live fence in S Yunnan and is cultivated as a potted plant in C and N China. It is used medicinally.