4. Lepidium austrinum Small, Fl. S.E. U.S. 468, 1331. 1903.
Lepidium austrinum var. orbiculare Thellung; L. lasiocarpum var. orbiculare (Thellung) C. L. Hitchcock
Annuals or biennials; often densely hirsute, (trichomes cylindrical). Stems often simple from base, erect, branched distally, (1.5-)2-6.7(-9.4) dm. Basal leaves (later withered); rosulate; petiole (0.7-) 1.5-4.5 cm; blade pinnatifid, 2-8.3 cm × 9-26 mm, margins (of lobes) entire or dentate. Cauline leaves shortly petiolate; blade oblanceolate to nearly linear, 1-4.5 (-6.2) cm × 3-10(-17) mm, base attenuate to cuneate, not auriculate, margins entire or dentate. Racemes much-elongated in fruit; rachis pubescent, trichomes curved, with fewer and longer, straight ones. Fruiting pedicels usually divaricate, rarely horizontal, straight or slightly recurved, (terete), (2.5-)3-4.1(-4.7) × 0.2 mm, puberulent adaxially. Flowers: sepals oblong, 0.8-1 × 0.2-0.4 mm; petals (sometimes absent), white, oblanceolate, 0.4-1.6 × 0.1-0.8 mm, claw absent; stamens 2, median; filaments 0.8-1 mm; anthers 0.1-0.2 mm. Fruits elliptic-obovate to obovate-orbicular, 2.4-3.2 × 1.8-2.5 mm, apically winged, apical notch 0.2-0.5 mm deep; valves thin, smooth, not veined, sparsely puberulent, (trichomes often antrorsely appressed, sometimes restricted to margin); style 0.05-0.1 mm, included in apical notch. Seeds ovate, 1.4-1.6 × 0.7-0.9 mm.
Flowering Mar-Jun. Disturbed grounds, railroad tracks and embankments, fields, knolls, stream banks, waste areas, open banks, roadsides, sandy terraces; Kans., La., Miss., N.Mex., Okla., Tex.; Mexico (Coahuila, Nuevo León, San Luis Potosí).