Toothwort (Cardamine concatenata)
A plant whose whole life cycle, from bursting out of the ground through flowering and seeding and withering and back to dormancy, occupies about a month in the early spring. Toothworts are common in the woods around Pittsburgh, sometimes in great numbers. The deeply cut leaves are distinctive and easily set this plant apart from other members of the same group, such as the Broadleaf Toothwort and Spring Cress.
Gray puts the Toothworts in the genus Dentaria, and lists this one as Dentaria laciniata.
DENTARIA [Tourn.] L. TOOTHWORT. PEPPER-ROOT
Pod lanceolate, flat. Style elongated. Seeds in one row, wingless, the funiculus broad and flat. Cotyledons petioled, thick, very unequal, their margins somewhat infolding each other. —Perennials, of damp woodlands, with long fleshy sometimes interrupted scaly or toothed rootstocks, of a pleasant pungent taste; stems leafless below, bearing 2 or 3 petioled compound leaves about or above the middle, and terminated by a corymb or short raceme of large white or purple flowers. (Name from dens, a tooth.)
D. laciniata Muhl. Tubers deep-seated; stems pubescent above; cauline leaves 3, whorled or nearly so, the lateral leaflets deeply cleft, glabrous or pubescent, the segments linear to narrowly oblong, conspicuously gash-toothed; basal leaves, when present, similar; flowers white or purplish; calyx 6-9 mm. long; petals 1-2 cm. long. Rich damp woods, w. Que. and Vt. to Minn., and southw. Apr., early May.