Description from Flora of China
Ranunculus sect. Batrachium de Candolle, Syst. Nat. 1: 233. 1817.
Herbs perennial or annual, aquatic or semiterrestrial, with stems and leaves often submersed. Leaves alternate, subsessile to long petiolate, leaf blade usually submersed, 2--5 × dissected, ultimate segments filiform or narrowly linear, sometimes floating and then blade 3-lobed, not finely dissected. Inflorescence a solitary, leaf-opposed flower. Flowers bisexual, actinomorphic. Receptacle conical or subulate. Sepals (4 or)5, caducous. Petals (4 or)5, usually white, with yellow base, rarely entirely yellow, obovate, base shortly clawed, with a nectary pit above claw, apex rounded. Stamens few or numerous; anthers latrorse. Carpels numerous; ovule 1 per carpel. Style with adaxial stigmatic surface. Aggregate fruit ovoid or globose; achenes obovoid, slightly bilaterally compressed, transversely rugose.
The separation of Batrachium from Ranunculus is not clear-cut and many botanists prefer to include the former genus within the latter. All species are aquatic or grow on wet mud.
About 20 species: S Africa, Asia, SE Australia, Europe, North and South America; eight species (one endemic) in China.
(Authors: Wang Wencai; Michio Tamura)