3. Boechera atrorubens (Suksdorf ex Greene) Windham & Al-Shehbaz, Harvard Pap. Bot. 11: 64. 2006; Arabis atrorubens Suksdorf ex Greene, Erythea 1: 223. 1893; A. sparsiflora Nuttall var. atrorubens (Suksdorf ex Greene) Rollins, Res. Stud. State Coll. Wash. 4: 26. 1936. TYPE: United States, Washington, western Klickitat County, on rocky mountain summits, 17 May 1892, W. N. Suksdorf 2105 (holotype: WS!; isotypes: GH!, MO!, NY, 2U!, WS!).
Arabis atriflora Suksdorf, Deutsch. Bot. Monatsschr. 16: 211. 1898. TYPE: same as above.
Plants mostly short-lived perennials, with non-woody caudices, lacking crowded, persistent leaf bases; sexual, with ellipsoid pollen. Stems usually 1 per caudex branch, arising near ground surface from center of basal rosettes, 0.8–6.0 dm, lower parts with scattered, simple and short- stalked, 2-rayed trichomes 0.10–0.15 mm, upper parts glabrous. Leaves at stem bases oblanceolate, 4–10 mm wide, usually dentate, not ciliate, blade surfaces densely pubescent with short-stalked, 3–4-rayed trichomes 0.1–0.2 mm; cauline leaves 7–25, concealing stem proximally, the uppermost glabrous, with auricles 1–4 mm. Inflorescences mostly unbranched, 6–20-flowered; fruiting pedicels 5–10 mm, ascending, usually straight, glabrous or with spreading, simple trichomes. Flowers ascending at anthesis; sepals pubescent; petals dark reddish purple drying indigo, 7–9 ´ 1.5–2.0 mm, glabrous; ovules 80–100 per fruit. Fruits (4–)6–12 cm ´ 1.7–2.2 mm, ascending, not appressed to rachises, not secund, curved or straight, with parallel edges, glabrous; style 0.2–0.5 mm. Seeds uniseriate, 1.2–1.7 ´ 0.9–1.2 mm; wing distal and lateral, 0.1–0.2 mm wide.
Habitat: rocky summits and sandy loam on sagebrush slopes.
Elevation: ca. 600 m.
Distribution: United States (Oregon, Washington).
Reproductive mode: sexual diploid.