Hecatonia palustris Loureiro; Ranunculus holophyllus Hance; R. oryzetorum Bunge; R. sceleratus var. sinensis H. Léveillé.

Herbs annual. Roots fibrous, subequally thick. Stems 10--75 cm, glabrous or sparsely puberulent, branched above. Basal leaves 5--13; petiole 1.2--15 cm, subglabrous or sparsely pubescent; blade 3-partite, pentagonal, reniform, or broadly ovate, or broadly ovate, 1--4 × 1.5--5 cm, papery or herbaceous, glabrous or abaxially puberulent, base broadly cordate, central lobe cuneate or rhombic, 3-lobed, lobules 1- or 2-denticulate or entire; lateral lobes obliquely broadly obovate or obliquely cuneate, unequally 2-lobed or 2-cleft to middle. Lower stem leaves similar to basal ones; upper stem leaves short petiolate, cuneate at base, 3-sect, segments oblanceolate. Compound monochasi um terminal, corymbose; bracts leaflike. Flowers 0.4--0.8 cm in diam. Pedicel 0.5--1.5 cm, glabrous or sparsely puberulent. Reeptacle puberulent or glabrous. Sepals 5, ovate-elliptic, 2--3 mm, abaxially appressed puberulent or glabrous. Petals 5, obovate, 2.2--4.5 × 1.4--2.4 mm, nectary pit without a scale, apex rounded. Stamens 10--19; anthers ellipsoid. Aggregate fruit cylindric, 3--11 × 1.5--4 mm; carpels numerous. Achene slightly bilaterally compressed, obliquely obovoid, 1--1.1 × 0.8--1 mm, glabrous, sometimes transversely 2- or 3-rugose, somewhat turgid along sutures; stigmas persistent, ca. 0.1 mm. Fl. Jan--Jul.

By streams or lakes, paddy fields, wet grassy places; 50--2300 m. Anhui, Fujian, Gansu, Guangdong, Guangxi, Guizhou, Hebei, Heilongjiang, Henan, Hunan, Jiangsu, Jiangxi, Jilin, Liaoning, Nei Mongol, Ningxia, Shaanxi, Shandong, Shanxi, Sichuan, Taiwan, Xinjiang, Yunnan, Zhejiang [Afghanistan, Bhutan, N India, Japan, Kazakhstan, Korea, Nepal, N Pakistan, Russia (Siberia), Thailand; SW Asia, Europe, North America].