1. Boechera acutina (Greene) Windham & Al-Shehbaz, Harvard Pap. Bot. 12: 236. 2007.
Arabis acutina Greene, Leafl. Bot. Observ. Crit. 2: 82. 1910; A. divaricarpa A. Nelson var. interposita (Greene) Rollins; A. drummondii A. Gray var. interposita (Greene) Rollins; A. interposita Greene
Biennials or perennials; short-lived; apomictic; caudex present or absent. Stems usually 1 per caudex branch, arising from center of rosette near ground surface, 1.5-6 dm, densely pubescent proximally, trichomes sessile, 2-4-rayed, 0.15-0.4 mm, usually sparsely pubescent distally, rarely glabrous. Basal leaves: blade oblanceolate, 1.5-6 mm wide, margins usually entire, rarely denticulate, ciliate proximally, trichomes (simple), to 0.5 mm, surfaces sparsely to moderately pubescent, trichomes sessile, 3-5 (or 6)-rayed, 0.15-0.35 mm. Cauline leaves: 2-20(-38), often concealing stem proximally; blade auricles 0.3-2 mm, surfaces of distalmost leaves sparsely pubescent or glabrous. Racemes 5-20(-36)-flowered, usually unbranched. Fruiting pedicels erect to ascending, usually straight, 3-10 mm, pubescent or glabrous, trichomes appressed, branched. Flowers ascending at anthesis; sepals pubescent; petals white or lavender, 5-7 × 0.9-1.3 mm, glabrous; pollen spheroid. Fruits ascending, not appressed to rachis, not secund, straight, edges parallel, 2.5-7.5 cm × 1.2-1.8 mm; valves glabrous; ovules 46-100 per ovary; style 0.3-1 mm. Seeds uniseriate, 1.8-2.2 × 1-1.4 mm; wing continuous, 0.1-0.4 mm wide.
Flowering Jun-Jul. Gravelly slopes in meadows, open forests; 1400-1900 m; Calif., Idaho, Oreg.
Boechera acutina is an apomictic hybrid that clearly contains a genome derived from B. stricta; the other parent remains uncertain. Plants of B. acutina are superficially similar to B. pratincola and are often misidentified as Arabis (Boechera) divaricarpa; the species is easily distinguished from both of those (see M. D. Windham and I. A. Al-Shehbaz 2007b for detailed comparison).