Boechera collinsii |
Boechera shevockii |
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collin's suncress, Collins' rockcress |
Shevock's rockcress |
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Habit | Perennials; usually short-lived; sexual; caudex not woody. | Perennials; long-lived; (pulvinate); sexual; caudex woody (with persistent, crowded leaf bases). |
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. |
1 per caudex branch, arising from center of rosette near ground surface, 0.5–1 dm, puberulent proximally, trichomes (scattered), simple, 0.02–0.1 mm, similarly pubescent 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 oblong-oblanceolate, 1–2 mm wide, margins entire, ciliate distally, trichomes (simple), 0.02–0.1 mm, surfaces glabrous. |
Cauline leaves | (8–)15–40, concealing stem proximally; blade auricles 1–3 mm, surfaces of distalmost leaves usually sparsely pubescent. |
3–7, not concealing stem; blade auricles absent, surfaces of distalmost leaves glabrous. |
Racemes | (15–)30–90-flowered, usually unbranched. |
4–7-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 glabrous; petals lavender, 4–5 × 1–1.2 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, 5–9 mm, glabrous. |
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. |
ascending, not appressed to rachis, not secund, straight, edges parallel, 2.5–3 cm × 1–1.5 mm; valves glabrous; ovules 30–34 per ovary; style ca. 0.5 mm. |
Seeds | uniseriate, 1–1.4 × 0.8–1 mm; wing continuous (rarely absent), to 0.1 mm wide. |
uniseriate, ca. 1.2 × 0.8 mm; wing distal or continuous, ca. 0.1 mm wide. |
2n | = 14. |
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Boechera collinsii |
Boechera shevockii |
|
Phenology | Flowering May–Jun. | Flowering Jun. |
Habitat | Rocky and gravelly hillsides, prairies, open woods, floodplains | Ledges of rock outcrops |
Elevation | 600-1400 m (2000-4600 ft) | ca. 2500 m (ca. 8200 ft) |
Distribution |
ID; MN; MT; ND; NE; SD; WY; AB; MB; QC; SK
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CA |
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 shevockii is a close relative of B. davidsonii, from which it is readily distinguished by having puberulent (versus glabrous) stems, shorter (4–5 versus 6–10 mm) petals, and much shorter (5–7 versus 30–80 mm) basal leaves. It is known only from the type specimen, from the southern Sierra Nevada in Tulare County. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 370. | FNA vol. 7, p. 406. |
Parent taxa | Brassicaceae > tribe Boechereae > Boechera | Brassicaceae > tribe Boechereae > Boechera |
Sibling taxa | ||
Synonyms | Arabis collinsii, Arabis holboellii var. collinsii, Arabis retrofracta var. collinsii | |
Name authority | (Fernald) Á. Löve & D. Löve: Taxon 31: 125. (1982) | Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 82. (2006) |
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