Cut-Leaf Toothworts are common in rich open woods; this one was blooming on a wooded hillside in Mount Lebanon in late April. The leaves are distinctive: they grow in whorls of three, and they are narrow and deeply divided, with jagged teeth on each lobe. The flowers of Broadleaf Toothwort (Cardamine diphylla) are similar, but the leaves are very different.
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.