5. Euphorbia hypericifolia Linnaeus, Sp. Pl. 2: 454. 1753.
通奶草 tong nai cao
Herbs, annual, 15-30 cm tall. Root fibrous, 2-3.5 mm thick. Stems branched mainly from upper parts, erect, 1-3 mm thick, glabrous or sparsely pilose. Leaves opposite; stipules triangular, 1.3-1.5 mm, free or connate; petiole 1-2 mm; leaf blade narrowly oblong or obovate, 1-2.5 cm × 4-8 mm, adaxially dark green, light green abaxially, sometimes purple-red, sparsely pilose on both surfaces, or glabrescent abaxially, base rounded, margin entire or finely serrulate toward apex, apex obtuse or rounded; involucral leaves 2, similar to normal leaves. Cyathia many in axillary or terminal cymes, peduncle 3-5 mm; involucre turbinate, ca. 1 × 1 mm, marginal lobes 5, ovate-triangular; glands 4, appendages white or light pink. Male flowers numerous, slightly exserted from involucre. Female flower: pedicel longer than involucre; ovary 3-angular, glabrous; styles free; stigma slightly 2-lobed. Capsule 3-angular, 1-1.5 × ca. 2 mm, smooth, glabrous. Seeds ovoid-angulate, ca. 1.2 × 0.8 mm, each side with several striae; caruncle absent. Fl. and fr. Aug-Dec. 2n = 32*.
Fields, roads, scrub. Beijing, Guangdong, Guangxi, Guizhou, Hainan, Hunan, Jiangxi, Sichuan, Taiwan, Yunnan [New World; naturalized in many parts of the Old World].
This species is used medicinally. It has been much confused with Euphorbia indica but that species differs by the puberulent stems and capsules (see Raju & Rao, Indian J. Bot. 2: 202. 1979).