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Amphibious, annual herb, from slender, fleshy roots; stems 1 to several, erect, 15-50 cm tall, usually branched, smooth, hollow.
Basal and stem leaves kidney-shaped to semi-circular, deeply 3-lobed or 3-parted, 1-5 cm long, 1.5-7 cm wide, bases squared-off to heart-shaped, the segments again lobed or parted, sometimes undivided, margins round-toothed to -lobed, tips rounded or sometimes blunt, the stalks 2- to 4-times length of blade; stem leaves alternate, numerous, more deeply lobed and divided than basal leaves.
Inflorescence of few- to many-flowered cymes terminal to main stem and branches, the flower stalks stout, 1-3 cm long; receptacle hairy or smooth; petals 3-5, distinct, yellow, 2-5 mm long, 1-3 mm wide, egg-shaped, nectary on upper surface, the nectary scale about 1 mm long, not covering nectary; sepals 3-5, yellowish, bent back from near base, 2-5 mm long, 1-3 mm wide, smooth or sparsely stiff-hairy, early deciduous; stamens 15 to 20; pistils (50) 100-250 (or more).
Achenes, numerous in an elliptic to cylindric head 5-13 mm long, 3-7 mm wide, the achenes egg-shaped, slightly flattened, 1-1.2 mm long, 0.8-1 mm wide, thick-margined, smooth or corrugated; beaks stout, triangular, usually straight, 0.1 mm long.
The introduced var. sceleratus, with more deeply cleft basal leaves and cross-corrugated achene faces, is known in the Osoyoos area.
Source: The Illustrated Flora of British Columbia