Pod a short silique or a silicle, varying from oblong-linear to globular, terete or nearly so; valves strongly convex, nerveless. Seeds usually numerous, small, turgid, marginless, in 2 irregular rows in each cell (except in N. sylvestre). Cotyledons accumbent.—Aquatic or marsh plants, with yellow or white flowers, and commonly pinnate or pinnatifid leaves, usually glabrous. (Name from Nasus tortus, a convulsed nose, alluding to the effect of its pungent qualities.)
§ 1. Petals white, twice the length of the calyx; pods linear; leaves pinnate.
N. officinàle, R. Br. (True Water-Cress.) Perennial; stems spreading and rooting; leaflets 3–11, roundish or oblong, nearly entire; pods (6–8´´ long) ascending on slender widely spreading pedicels.—Brooks and ditches; escaped from cultivation. (Nat. from Eu.)
§ 2. Petals yellow or yellowish, seldom much exceeding the calyx; pods linear, oblong, or even ovoid or globular; leaves mostly pinnatifid.
[*] Perennial from creeping or subterranean shoots; flowers rather large, yellow.
N. sylvéstre, R. Br. (Yellow Cress.) Stems ascending; leaves pinnately parted, the divisions toothed or cut, lanceolate or linear; pods (½´ long) on slender pedicels, linear and narrow, bringing the seeds into one row; style very short.—Wet meadows, Mass. to Va.; rare. (Nat. from Eu.)
1. N. sinuàtum, Nutt. Stems low, diffuse; leaves pinnately cleft, the short lobes nearly entire, linear-oblong; pods linear-oblong (4–6´´ long), on slender pedicels; style slender.—Banks of the Mississippi and westward. June.
[*][*] Annual or biennial, rarely perennial (?), with simple fibrous roots; flowers small or minute, greenish or yellowish; leaves somewhat lyrate.
2. N. sessiliflòrum, Nutt. Stems erect, rather simple; leaves obtusely incised or toothed, obovate or oblong; flowers minute, nearly sessile; pods elongated-oblong (5–6´´ long), thick; style very short.—W. Ill. to E. Kan., Tenn., and southward. April–June.
3. N. obtùsum, Nutt. Stems much branched, diffusely spreading; leaves pinnately parted or divided, the divisions roundish and obtusely toothed or repand; flowers minute, short-pedicelled; pods longer than the pedicels, varying from linear-oblong to short-oval; style short.—With n. 1 and 2.