77. Boechera polyantha (Greene) Al-Shehbaz, Harvard Pap. Bot. 11: 78. 2006; Arabis polyantha Greene, Leafl. Bot. Observ. Crit. 2: 80. 1910. TYPE: United States, Washington, Douglas County, along R.R. track at Rock Island, 23 Apr 1899, K. Whited 1043 (holotype, US!; isotype, WS!).
Arabis macdougalii Rydb., Bull. Torrey Bot. Club 39: 326. 1912. TYPE: United States, Montana, Missoula County, Old Sentinel, mountain near Missoula, 12 Jun 1901, 1500 m, D. T. MacDougal 191 (holotype, NY!; isotypes, CAN!, K!, NY!, US!).
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 rosette, 2.5–9.0 dm, lower parts with many short-stalked, 2–6-rayed trichomes 0.1–0.7 mm, upper parts similarly pubescent. Leaves at stem bases oblanceolate, 1.5–7.0 mm wide, entire or shallowly dentate, ciliate at base of petiole with trichomes to 0.9 mm, blade surfaces densely pubescent with short-stalked, 5–10-rayed trichomes 0.10–0.25 mm; cauline leaves 16–42, concealing stem proximally, the uppermost pubescent, with auricles 0.5–1.5 mm. Inflorescences mostly unbranched, 17–96-flowered; fruiting pedicels 7–13 mm, reflexed, abruptly recurved at base but otherwise straight, with appressed, branched trichomes. Flowers descending at anthesis; sepals pubescent; petals white, 6–9 ´ 1.0–2.5 mm, sparsely pubescent abaxially; ovules 74–110 per fruit. Fruits 3.5–7.2 cm ´ 1.2–1.5 mm, strongly reflexed, usually appressed to rachises, occasionally somewhat secund, straight, with parallel edges, densely pubescent; styles 0.05–0.20 mm. Seeds uniseriate, 0.9–1.2 ´ 0.7–1.0 mm; wing continuous, 0.05–0.10 mm wide.
Habitat: rocky, gravelly, and sandy slopes in open areas.
Elevation: 900–2450 m.
Distribution: United States (Idaho, Montana, Oregon, Washington).
Reproductive mode: sexual diploid.