Cardamine longii Fernald, Rhodora 19: 91. 1917. TYPE:

Herbs, perennial, glabrous throughout. Rhizomes slender, cylindrical, 0.8–1.5 mm in diam.; stolons absent. Stems 0.5–4(–6) dm, prostrate to decumbent or erect, simple or branched, glabrous. Rhizomal leaves absent; cauline leaves 3–10, simple or rarely 3–5-foliolate, somewhat fleshy; petiole 0.4–2.5 cm, base not auriculate; leaf blade or terminal leaflet of compound leaves orbicular to reniform or ovate to oblong, 0.4–3 × 0.3–2 cm, base subcordate to rounded or subtruncat, margin entire or repand or rarely undulate, apex rounded; lateral leaflets (when present) similar to terminal one but considerably smaller, sessile or with a petiolule to 2 mm. Racemes ebracteate; fruiting pedicels divaricate-ascending to spreading, 0.5–2(–4) mm. Sepals ovate, 0.7–1.2 × 0.5–0.7 mm, erect, base of lateral pair not saccate; petals absent or rudimenatary and to 0.7 mm; filaments 0.5–0.8 mm; anthers ovate, 0.1–0.2 mm. Fruit narrowly oblong to linear, (3–)5–10(–15) × 0.8–1.2 mm; valves glabrous; style 0.2–0.5(–1) mm; ovules and seeds 6–22 per fruit. Seeds light or yellowish brown, oblong or ovate, 1–1.4 × 0.7–1 mm.

Flowering: Jun–Sep.

Habitat: tidal marshes, mud flats, tidal shores of rivers, shallow water, swampy areas, shady rocky crevices covered at high tide.

Elevation: sea level.

Distribution: United States (Florida, Maine, Maryland, Massachusetts, New Jersey, New York, North Carolina, South Carolina, Virgina).