* Flowers white.
N. officinale: stem much branched, short and creeping, or floating in shallow water; leaves pinnate, with distinct segments, the terminal one usually larger, ovate or orbicular; flowers small, white, in short racemes; pods 6-8 lines long, on spreading pedicels, slightly curved upwards. - The common edible Water-cress. - Brooks and rivulets. Fl. all the Summer.
** Flowers yellow. † Pods half an inch long or more.
N. sylvestre: stem creeping, the flowering branches erect or ascending, a foot high or more; leaves deeply pinnatifid or almost pinnate, the lower lobes distinct and narrow, the terminal one often larger and broader; flowers small, yellow, the petals twice as long as the calyx; pod slender. - River-banks and wet places. Fl. June to September.
†† Pods not exceeding a quarter of an inch in length.
N. palustre: stem creeping, but weaker and not so tall as the last; leaves deeply pinnatifid, the lobes broader and more toothed; flowers small, yellow, the petals seldom exceeding the calyx; pod about three lines long, slightly curved. - Muddy and watery places. Fl. June to September.
N. amphibium: stem 2-3 feet, erect; leaves narrow lanceolate, 3-4 inches long, slightly toothed, more frequently deeply toothed or lobed, sometimes divided to the midrib into narrow segments; flowers yellow, the petals longer than the calyx: pod straight, elliptical, about two lines long. - Moist meadows and watery places. Fl. June to August.