Proc. Biol. Soc. Wash. 49: 147. 1936.
Perennials; (caudex usually simple, rarely branched, covered with persistent petiolar remains); sparsely to densely pubescent basally, trichomes short-stalked, cruciform or 3-rayed, stellate, (to 0.4 mm in diam.). Stems simple or few from caudex, erect, unbranched or rarely branched (few) distally, (1–)1.5–4(–5) dm, (glabrous throughout or sparsely pubescent proximally). Basal leaves: petiole 0.5–2.5(–3) cm; blade oblanceolate to obovate, (0.6–)1–3.5(–4.5) cm × (3–)5–15(–20) mm, margins entire or dentate, (not ciliate), apex obtuse, surfaces uniformly pubescent, trichomes short-stalked, stellate. Cauline leaves 3 or 4(–6); blade linear, oblong or oblanceolate, 1–3(–4) cm × (1.5–)3–7(–10) mm, base cuneate, not auriculate, margins usually entire, rarely few-toothed, apex obtuse, surfaces glabrous or sparsely pubescent at least along margin. Racemes simple. Fruiting pedicels ascending to divaricate, (5–)8–20 mm, (glabrous). Flowers: sepals (greenish), oblong, 2.5–4 × 1–1.5 mm, lateral pair saccate basally; petals white, oblanceolate, 7–9 × 2.5–3.5 mm, apex rounded; filaments 2.5–4 mm; anthers oblong, 0.8–1 mm; (gynophore to 0.5 mm). Fruits divaricate, slightly torulose, sometimes slightly curved, slightly flattened, (1.3–)1.7–3.5(–4) cm × 1–1.5 mm; valves each with obscure midvein extending to middle; ovules 14–28 per ovary; style 0.5–1.3 mm. Seeds not winged, oblong, 1–1.2 × 0.5–0.6 mm. 2n = 32.
Phenology: Flowering Apr–Jun.
Habitat: Open woods, rocky bluffs, steep banks, canyon margins
Elevation: 400-1800 m
Idaho, Oreg., Wash.
Arabis crucisetosa is known from Idaho, Lewis, and Nez Perce counties in Idaho, from Wallowa County in Oregon, and from Asotin County in Washington.