黑水大戟 hei shui da ji

Herbs, annual, 15-40(-90) cm tall. Rootstock a slender taproot, 3-6 cm × 1-4 mm thick, unbranched, with few small fibrous rootlets. Stems single, 2-4 cm, branched at top. Leaves alternate; stipules absent; petiole almost absent; leaf blade linear or linear-elliptic, 2-6 × 0.3-0.5 cm, base attenuate, margin entire, apex rounded. Cyathium stipe ca. 2 mm; involucre campanulate, ca. 2.5 × 2 mm, shortly pubescent outside, lobes ovate, ciliate; glands 4, transversely oblong. Male flowers small, not exserted from involucre. Female flower: ovary densely tuberculate; styles free, persistent; style arms unlobed. Capsule trigonous-ovoid, ca. 3 × 3 mm, with vertical furrows, densely tuberculate. Seeds ovoid, ca. 2.2 × 1.5 mm, yellow, smooth and shiny; caruncle subulate, deep yellow, sessile, easily lost. Fl. and fr. May-Jul.

● Roadsides; ca. 2000 m. Gansu (Maiji Shan), Sichuan (Heishui).