17. Boechera cusickii (S. Watson) Al-Shehbaz, Novon 13: 384. 2003; Arabis cusickii S. Watson, Proc. Amer. Acad. Arts 17: 363. 1882. TYPE: United States, Oregon, Union Co., rocky ridges, early spring 1879, W. C. Cusick 727 (holotype, GH!; isotypes, K!, NY!, OSC!, US!).
Plants long-lived, often cespitose perennials, with mostly 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, 1.0–2.5(–3.8) dm, lower parts with abundant, simple trichomes 0.5–1.5 mm, upper parts sparsely pubescent or glabrous. Leaves at stem bases linear to narrowly oblanceolate, 0.5–2.0 mm wide, entire, ciliate with simple trichomes 1.0–1.7 mm, blade surfaces moderately pubescent with simple and long-stalked, 2-rayed trichomes 0.5–1.7 mm; cauline leaves 10–30, often concealing stem proximally, the uppermost sparsely pubescent, with auricles to 0.5 mm or lacking. Inflorescences mostly unbranched, 5–14-flowered; fruiting pedicels 4–15(–20) mm, ascending, straight, glabrous or with few simple trichomes. Flowers ascending at anthesis; sepals pubescent; petals white to lavender, 6–10 ´ 2–3 mm, glabrous; ovules 56–106 per fruit. Fruits 4–8(–9.5) cm ´ 2.3–3.0 mm, ascending to divaricate-ascending, not appressed to rachises, not secund, straight or curved, with parallel edges, glabrous; style 0.1–0.5 mm. Seeds uniseriate, 1.5–2.5 ´ 1.5–2.0 mm; wing continuous, 0.1–0.2 mm wide.
Habitat: basaltic bluffs, rocky slopes, rock crevices, gravelly hillsides, sagebrush hills, outcrops of volcanic rock.
Elevation: 600–1800 m.
Distribution: United States (Idaho, Nevada, Oregon, Washington).
Reproductive mode: sexual diploid.