23. Boechera drepanoloba (Greene) Windham & Al-Shehbaz, Harvard Pap. Bot. 11: 263. 2007; Arabis drepanoloba Greene, Pittonia 3: 306. 1898; A. lemmonii S. Watson var. drepanoloba (Greene) Rollins, Rhodora 43: 384. 1941. TYPE: Canada, Alberta, Banff National Park, Devil’s Head Lake, 51˚15' N, 115˚25' W, 6 Aug 1891, J. Macoun 1719a (holotype, NDG!; isotypes, CAN!, NY!, US!).
Arabis oreophila Rydberg, Bull. Torrey Bot. Club 34: 437. 1907; A. drummondii A. Gray var. oreophila (Rydberg) M. Hopkins, Rhodora 39: 141. 1937. TYPE: United States, Utah, Wasatch/Salt Lake Cos., divide between Big Cottonwood Canyon and Heber Valley, 5 Jul 1905, P. A. Rydberg & E. C. Carlton 6678 (holotype, NY!).
Plants short- to long-lived perennials, with mostly non-woody caudices, lacking crowded, persistent leaf bases; apomictic, with spheroid pollen. Stems usually 1 per caudex branch, arising near ground surface from center of basal rosettes, 1–4 dm, lower parts glabrous or with few sessile or subsessile, 2–3-rayed trichomes 0.1–0.3 mm, upper parts glabrous. Leaves at stem bases oblanceolate, 2–6 mm wide, entire, ciliate on petioles with submalpighiaceous or simple trichomes to 0.6 mm, blade surfaces sparsely to densely pubescent with subsessile, 2–6-rayed trichomes 0.1–0.3 mm; cauline leaves 3–15, often concealing stem proximally, the uppermost usually glabrous, with auricles 0.7–2.5 mm. Inflorescences mostly unbranched, 5–25-flowered; fruiting pedicels 4–8 mm, horizontal to ascending, straight or curved, glabrous. Flowers ascending at anthesis; sepals glabrous or with scattered trichomes; petals purple to lavender, 6–8 ´ 1.5–2.5 mm, glabrous; ovules 44–76(–104) per fruit. Fruits 3.0–5.8 cm ´ 2.0–3.5 mm, horizontal to ascending, secund, straight to slightly curved, with parallel edges, glabrous; style 0.05–0.50 mm. Seeds subbiseriate, 1.5–2.2 ´ 1.2–1.6 mm; wing continuous, 0.3–0.7 mm wide.
Habitat: rocky slopes and talus in alpine and subalpine habitats.
Elevation: 2050–3800 m.
Distribution: Canada (Alberta), United States (Alaska, Colorado, Idaho, Montana, Oregon, Utah, Washington, Wyoming).
Reproductive mode: apomictic triploid.