Perennials; (submerged aquatic, rooting from proximal nodes, forming clumps); glabrous or pubescent proximally on young leaves. Stems prostrate basally (hollow), branched, (2–)4–12(–13) dm. Basal leaves not rosulate; blade margins pinnatifid. Cauline leaves (proximal) petiolate, (distal) sessile; blade pectinate or pinnatisect to pinnatifid (especially when submerged), oblanceolate to elliptic, 4–12 cm × 5–30 mm, base auriculate or not, margins entire or denticulate to serrate (emergent ones usually undivided, rarely lobed). Racemes considerably elongated. Fruiting pedicels horizontal to reflexed, straight or recurved, (5–)7–15(–18) mm. Flowers: sepals erect, oblong, 2.5–3.5 × 1–1.7 mm; petals yellow, obovate, (3.3–)3.8–5.5(–6.2) × 1.5–2.5 mm; median filaments 3–4 mm; anthers ovate, 0.7–1 mm. Fruits silicles, straight, ovoid-oblong, (2.5–)3–5.5(–7) × 1.7–2.7(–3) mm; valves glabrous; ovules 36–62 per ovary; style (0.5–)1–2.2(–2.5) mm. Seeds biseriate, reddish brown, ovoid, 0.7–1 mm (0.5–0.6 mm diam.), colliculate. 2n = 16, 32.

Phenology: Flowering Jun–Aug.
Habitat: Lakeshores, marshes, ponds, streams

Distribution

• Generated Map
• Legacy Map

Que., Maine, N.Y., Europe, Asia.

Discussion

Selected References

None.

Lower Taxa

None.