Boechera collinsii |
Boechera koehleri |
|
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collin's suncress, Collins' rockcress |
Koehler's rockcress, shrubby rock-cress |
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Habit | Perennials; usually short-lived; sexual; caudex not woody. | Perennials; long-lived; sexual; caudex woody (with persistent, peg-like 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. |
usually 1 per caudex branch, arising from center of rosette, elevated above ground surface on woody base, 0.8–4.5 dm, pubescent proximally, trichomes stalked, 2–4-rayed, to 0.5 mm, mixed with simple ones, to 1 mm, glabrous 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 narrowly oblanceolate, 1–3 mm wide, margins entire, ciliate proximally, trichomes (simple), to 1 mm, surfaces moderately to sparsely pubescent, trichomes stalked, 2–4-rayed, 0.1–0.3(–0.5) mm. |
Cauline leaves | (8–)15–40, concealing stem proximally; blade auricles 1–3 mm, surfaces of distalmost leaves usually sparsely pubescent. |
3–17(–30), rarely concealing stem; blade auricles 0.5–2.5 mm, surfaces of distalmost leaves glabrous. |
Racemes | (15–)30–90-flowered, usually unbranched. |
6–20(–35)-flowered, usually 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 deep purple to magenta, 8–12 × 2.5–4 mm, glabrous; pollen ellipsoid. |
Fruiting pedicels | reflexed, abruptly recurved at base, otherwise straight, 4–13 mm, glabrous or sparsely pubescent, trichomes usually simple. |
divaricate-ascending to horizontal, straight, 10–18 mm, glabrous or sparsely pubescent, trichomes spreading, simple and 2-rayed. |
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 to widely pendent, not appressed to rachis, not secund, usually curved, rarely straight, edges parallel, 5–7.5 cm × 1.8–2.5 mm; valves glabrous; ovules 58–94 per ovary; style 0.05–0.2 mm. |
Seeds | uniseriate, 1–1.4 × 0.8–1 mm; wing continuous (rarely absent), to 0.1 mm wide. |
uniseriate, 1.3–1.8 × 1.2–1.5 mm; wing continuous, 0.1–0.2 mm wide. |
2n | = 14. |
|
Boechera collinsii |
Boechera koehleri |
|
Phenology | Flowering May–Jun. | Flowering Apr–May. |
Habitat | Rocky and gravelly hillsides, prairies, open woods, floodplains | Serpentine and limestone outcrops |
Elevation | 600-1400 m (2000-4600 ft) | 100-500 m (300-1600 ft) |
Distribution |
ID; MN; MT; ND; NE; SD; WY; AB; MB; QC; SK
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CA; OR
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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 koehleri var. koehlerei is in the Center for Plant Conservation’s National Collection of Endangered Plants. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 370. | FNA vol. 7, p. 386. |
Parent taxa | Brassicaceae > tribe Boechereae > Boechera | Brassicaceae > tribe Boechereae > Boechera |
Sibling taxa | ||
Synonyms | Arabis collinsii, Arabis holboellii var. collinsii, Arabis retrofracta var. collinsii | Arabis koehleri, Arabis arbuscula, Arabis koehleri var. stipitata |
Name authority | (Fernald) Á. Löve & D. Löve: Taxon 31: 125. (1982) | (Howell) Al-Shehbaz: Novon 13: 386. (2003) |
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