12. Boechera collinsii (Fernald) Á. Löve & D. Löve, Taxon 31: 125. 1982; Arabis collinsii Fernald, Rhodora 7: 32. 1905; A. holboellii Hornemann var. collinsii (Fernald) Rollins, Rhodora 43: 445. 1941; A. retrofracta Graham var. collinsii (Fernald) B. Boivin, Canad. Field-Naturalist 65: 17. 1951. TYPE: Canada, Quebec, Rimouski County, E of Baptiste Michaud’s, Bic, 16 & 18 Jul 1904, J. F. Collins & M. L. Fernald s.n. (holotype, GH!; isotypes, CAN!, DAO!, NY!).

     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, (1.5–)2.5–8.0 dm, lower parts with abundant, simple and short-stalked, 2-rayed trichomes to 1 mm, upper parts sparsely pubescent or glabrous. Leaves at stem bases oblanceolate, 1–7 mm wide, entire to dentate, ciliate along petioles with simple trichomes to 0.7 mm, blade surfaces moderately to densely pubescent with short-stalked, 5–8-rayed trichomes 0.15–0.4 mm; cauline leaves (8–)15–40, concealing stem proximally, the uppermost usually sparsely pubescent, with auricles 1–3 mm. Inflorescences mostly unbranched, (15–)30–90-flowered; fruiting pedicels 4–13 mm, reflexed, abruptly recurved at base but otherwise straight, glabrous or with few, mostly simple trichomes. Flowers descending to pendent at anthesis; sepals pubescent; petals white or rarely lavender, 4–6 ´ 0.8–1.5 mm, glabrous; ovules 70–126 per fruit. Fruits 3.5–6.0 cm ´ 0.9–1.5 mm, strongly reflexed, usually appressed to rachises, rarely somewhat secund, straight, with parallel edges, glabrous; style 0.2–0.5 mm. Seeds uniseriate, 1.0–1.4 ´ 0.8–1.0 mm; wing continuous (rarely absent), to 0.1 mm wide. 2n = 14.

Flowering: May–Jun.

Habitat: rocky and gravelly hillsides, prairies, open woods, and floodplains.

Elevation: 600–1400 m.

Distribution: Canada (Alberta, Manitoba, Quebec, Saskatchewan), United States (Idaho, Minnesota, Montana, Nebraska, North Dakota, South Dakota, Wyoming).

Reproductive mode: sexual diploid.