12. Ranunculus laxicaulis (Torr. & A. Gray) Darby (water-plantain, spearwort)

Pl. 520 a–c; Map 2378

Plants annuals. Roots not tuberous. Stems 15–80 cm long, erect or ascending, but often weak or reclining in aquatic habitats, often rooting at the lower nodes, glabrous or uncommonly sparsely hairy, without bulbils, the base not bulbous. Basal leaves usually absent at flowering, when present long-petiolate, the blade 1.0–4.5 cm long, 0.6–1.8 cm wide, oblong to ovate, simple, the base rounded to truncate, truncate or angled to a bluntly pointed tip, the margins entire or shallowly toothed, the teeth mostly bluntly pointed at their tips. Stem leaves mostly sessile, the blade 1.5–7.0 cm long, 0.4–2.0 cm wide, simple, ovate to lanceolate or narrowly elliptic, the uppermost leaf blades mostly linear to narrowly oblong-elliptic, the margins entire or few-toothed toward the tip. Sepals 4 or 5, 1.5–3.0 mm long, spreading or reflexed from the base (lacking a transverse fold), more or less plane. Petals 4–6(–10), 2–6 mm long, 1–2 mm wide, oblong, about as long as to somewhat longer than the sepals, yellow. Style present, but the apical portion usually shed after flowering. Head of achenes 2–4 mm long at maturity, hemispheric to globose or ovoid, the receptacle glabrous. Achenes 0.8–1.0 mm long, the dorsal margin bluntly to sharply keeled and sometimes very narrowly winged, the wall thick, smooth, glabrous, the beak 0.1–0.2 mm long, flattened, triangular, straight or bent to the side. April–September.

Scattered in the southern third of the state, also disjunct in St. Charles County (eastern [mostly southeastern] U.S. west to Kansas and Texas). Ponds, sinkhole ponds, streams, banks of rivers, sloughs, bottomland prairies, and wet swales and depressions of upland prairies and sand prairies; also ditches and wet roadsides; terrestrial or more commonly emergent aquatics, occasionally appearing floating-leaved.