3. Alchornea trewioides (Bentham) Müller Argoviensis, Linnaea. 34: 168. 1865.
红背山麻杆 hong bei shan ma gan
Shrubs, 1-3 m tall, dioecious. Branchlets puberulent or almost glabrous. Stipules subulate, 3-5 mm, pilose; petiole 7-12 cm; leaf blade broadly ovate, 8-15 × 7-13 cm, papery, abaxially puberulent along veins, base subcordate or subtruncate, with 4 glands, stipels lanceolate, 2-5 mm, margins serrulate or obscurely serrulate, apex acuminate or acute; basal veins 3. Male inflorescences axillary, often at leafless nodes, unbranched, 7-15 cm, puberulent; bracts triangular. Male flowers 3-15-fascicled; pedicel ca. 2 mm, glabrous; sepals 4, ca. 1.5 mm, glabrous; stamens (7 or)8. Female inflorescences terminal, unbranched, 5-6 cm, puberulent; bracts narrowly triangular, ca. 4 mm, base with 2 glands. Female flowers: pedicel ca. 1 mm; sepals 5-8, lanceolate, 2.5-4 mm, pubescent, sometimes one with basal gland; ovary globose, tomentulose; styles 3, filiform, connate at base. Capsule subglobose, 8-10 mm in diam., puberulent. Seeds compressed-ovoid, ca. 6 mm, brownish, tuberculate. Fl. Apr-May, fr. Jun-Aug.
Plains, mountains, slopes, thickets, open scrub, limestone hills; below 1200 m. Fujian, Guangdong, Guangxi, Hainan, S Hunan, S Jiangxi, Sichuan, SE Yunnan [Cambodia, Japan (Ryukyu Islands), Laos, N Thailand, N Vietnam].