Annuals; hirsute. Stems few to several from base, erect to ascending, or (outer ones) decumbent, unbranched, (0.15-) 0.3-1.3(-2.1) dm. Basal leaves (soon withered); not rosulate; petiole 0.5-2 cm; blade pinnatifid to pinnatisect (lobes linear to narrowly oblong), (1.5-)2.2-5.7(-7) cm × (0.5-)1-2(-3) mm, margins entire. Cauline leaves sessile; blade usually linear, rarely with linear lobes, 1-5 cm × 0.5-2 mm, base attenuate, not auriculate, margins entire. Racemes elongated, (dense) in fruit; rachis hirsute, trichomes straight, cylindrical. Fruiting pedicels erect to slightly ascending, straight and appressed to rachis or distally slightly recurved, (strongly flattened), (1.6-) 1.9-2.5(-3) × 0.4-0.8 mm (width proximal to apex), usually hirsute or, rarely, only adaxially. Flowers: sepals oblong to ovate, 0.7-1.1 × 0.2-0.6 mm; petals absent; stamens 4, median; filaments 0.5-1 mm; anthers ca. 0.1 mm. Fruits ovate, 2.5-3.5 × 2-2.8 mm, apically winged, apical notch (closed, often U-shaped), 0.5-0.7(-0.8) mm deep; valves thin, smooth, strongly reticulate-veined, usually hirsute, rarely glabrous; style absent or obsolete, included in apical notch. Seeds ovate, 1.2-1.8 × 0.8-1.2 mm. Flowering Mar-Jun. Margins of playas, saline areas, meadows, gypsum hills, dried pools, alkaline and clay flats and sinks, near hot springs, roadsides, borders of springs and ponds, sandy flats; 0-1600 m; Calif., Idaho, Nev., Oreg., Utah, Wash.; Mexico (Baja California).