Annuals; scapose. Stems (few to many from base), unbranched, (0.2–)0.5–2(–3) dm, pubescent proximally, glabrous distally, trichomes simple and 2(–4)-rayed, 0.1–0.4 mm. Basal leaves rosulate; petiolate; blade obovate, spatulate, oblanceolate, lanceolate, oblong, or, rarely, linear, 0.2–1.8(–3) cm × (0.5–)1–5(–10) mm, margins entire or 1–5-toothed on each side, surfaces pubescent with simple or stalked, 2–4-rayed trichomes, 0.1–0.5 mm. Cauline leaves 0. Racemes 4–20(–30)-flowered, ebracteate, usually considerably elongated in fruit; rachis usually flexuous, glabrous. Fruiting pedicels divaricate to ascending, straight or slightly curved upward, (2–)5–20(–35) mm, glabrous. Flowers: sepals (green or purplish), oblong, 1–2.5 mm, glabrescent or pubescent, (trichomes simple or 2-rayed); petals white, deeply 2-fid, (1.5–)2–4.5(–6) × 1–2 mm; anthers ovate, 0.2–0.4 mm. Fruits obovate, oblanceolate, lanceolate, elliptic, oblong, or linear, plane, flattened, (2.5–)4–9(–12) × 1.5–2.5(–3.5) mm; valves glabrous; ovules (20–)32–70(–84) per ovary; style 0.02–0.2 mm. Seeds ovoid (slightly flattened), 0.3–0.6(–0.8) × 0.2–0.4 mm. 2n = 14, 16, 20, 24, 28, 30, 32, 34, 36, 38, 40, 52, 54, 58, 60, 64.
