Boechera collinsii |
Boechera dispar |
|
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collin's suncress, Collins' rockcress |
pinyon rock cress |
|
Habit | Perennials; usually short-lived; sexual; caudex not woody. | Perennials; usually long-lived; sexual; caudex often woody. |
Stems | usually 1 per caudex branch, arising from center of rosette near ground surface, (1.5–)2.5–8 dm, densely pubescent proximally, trichomes simple and short-stalked, 2-rayed, to 1 mm, sparsely pubescent or glabrous distally. |
usually 1 per caudex branch, arising from center of rosette near ground surface, 0.9–3 dm, densely pubescent proximally, trichomes short-stalked, 5–12-rayed, 0.1–0.3 mm, sparsely pubescent to glabrescent distally. |
Basal leaves | blade oblanceolate, 1–7 mm wide, margins entire or dentate, ciliate along petiole, trichomes (simple), to 0.7 mm, surfaces moderately to densely pubescent, trichomes short-stalked, 5–8-rayed, 0.15–0.4 mm. |
blade linear-oblanceolate, 2–5 mm wide, margins entire, not ciliate, surfaces densely pubescent, trichomes short-stalked, 5–12(–16)-rayed, 0.1–0.3 mm. |
Cauline leaves | (8–)15–40, concealing stem proximally; blade auricles 1–3 mm, surfaces of distalmost leaves usually sparsely pubescent. |
1–5, not concealing stem; blade without auricles, surfaces of distalmost leaves pubescent. |
Racemes | (15–)30–90-flowered, usually unbranched. |
4–15(–20)-flowered, unbranched. |
Flowers | descending to pendent at anthesis; sepals pubescent; petals usually white, rarely lavender, 4–6 × 0.8–1.5 mm, glabrous; pollen ellipsoid. |
ascending at anthesis; sepals pubescent; petals purple to lavender, 3.5–6 × 1–1.5 mm, glabrous; pollen ellipsoid. |
Fruiting pedicels | reflexed, abruptly recurved at base, otherwise straight, 4–13 mm, glabrous or sparsely pubescent, trichomes usually simple. |
ascending, straight, 4–15(–25) mm, pubescent, trichomes appressed, branched. |
Fruits | strongly reflexed, usually appressed to rachis, rarely somewhat secund, straight, edges parallel, 3.5–6 cm × 0.9–1.5 mm; valves glabrous; ovules 70–126 per ovary; style 0.2–0.5 mm. |
divaricate-ascending, not appressed to rachis, not secund, straight, edges parallel, 4–7.3 cm × 2.7–4 mm; valves glabrous; ovules 44–52 per ovary; style 0.05–0.1 mm. |
Seeds | uniseriate, 1–1.4 × 0.8–1 mm; wing continuous (rarely absent), to 0.1 mm wide. |
uniseriate, 1.9–2.3 mm in diam.; wing continuous, 0.3–0.5 mm wide. |
2n | = 14. |
|
Boechera collinsii |
Boechera dispar |
|
Phenology | Flowering May–Jun. | Flowering Apr–May. |
Habitat | Rocky and gravelly hillsides, prairies, open woods, floodplains | Rocky slopes and gravelly soil in desert scrub and pinyon-juniper communities |
Elevation | 600-1400 m (2000-4600 ft) | 1500-2300 m (4900-7500 ft) |
Distribution |
ID; MN; MT; ND; NE; SD; WY; AB; MB; QC; SK
|
CA; NV |
Discussion | Though often treated as a variety of Arabis (Boechera) holboellii (e.g., R. C. Rollins 1993; G. A. Mulligan 1996), B. collinsii is easily distinguished from that species by having simple and 2-rayed (versus 4–8-rayed) trichomes proximally on stems, and narrower (0.9–1.5 versus 2–2.5 mm) usually non-secund fruits. The two taxa also show allopatric distributions, with B. collinsii found on the North American continent (usually east of the Rocky Mountains) and B. holboellii apparently confined to Greenland. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Boechera dispar is a distinctive sexual diploid that is known from Inyo, Mono, and San Bernardino counties, California, and Nye County, Nevada. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 370. | FNA vol. 7, p. 374. |
Parent taxa | Brassicaceae > tribe Boechereae > Boechera | Brassicaceae > tribe Boechereae > Boechera |
Sibling taxa | ||
Synonyms | Arabis collinsii, Arabis holboellii var. collinsii, Arabis retrofracta var. collinsii | Arabis dispar, Arabis juniperina, Arabis nardina, Arabis salubris |
Name authority | (Fernald) Á. Löve & D. Löve: Taxon 31: 125. (1982) | (M. E. Jones) Al-Shehbaz: Novon 13: 384. (2003) |
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