Boechera collinsii |
Boechera serpenticola |
|
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collin's suncress, Collins' rockcress |
serpentine rockcress |
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Habit | Perennials; usually short-lived; sexual; caudex not woody. | Perennials; long-lived; (cespitose); sexual; caudex 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, 0.5–1.8 dm, densely pubescent proximally, trichomes short-stalked, 5–8-rayed, 0.1–0.2, sparsely to moderately 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 narrowly oblanceolate, 1–2 mm wide, margins entire, ciliate along petiole, trichomes (branched), to 0.5 mm, surfaces densely pubescent, trichomes short-stalked, 5–8-rayed, 0.1–0.2 mm. |
Cauline leaves | (8–)15–40, concealing stem proximally; blade auricles 1–3 mm, surfaces of distalmost leaves usually sparsely pubescent. |
4–14, rarely concealing stem proximally; blade auricles 0.1–0.5 mm, surfaces of distalmost leaves densely pubescent. |
Racemes | (15–)30–90-flowered, usually unbranched. |
10–20-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, 6–8 × 1.5–2.5 mm, glabrous; pollen ellipsoid. |
Fruiting pedicels | reflexed, abruptly recurved at base, otherwise straight, 4–13 mm, glabrous or sparsely pubescent, trichomes usually simple. |
divaricate-descending or horizontal, nearly straight, 3–7 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. |
usually divaricate-descending or horizontal, rarely widely pendent, not appressed to rachis, not secund, straight or slightly curved, edges parallel, 3–4.5 cm × 2.5–3 mm; valves sparsely pubescent to glabrate; ovules 20–24 per ovary; style 1.5–2 mm. |
Seeds | uniseriate, 1–1.4 × 0.8–1 mm; wing continuous (rarely absent), to 0.1 mm wide. |
uniseriate, 2–2.5 × 1.5–1.8 mm; wing continuous, to 0.2 mm wide. |
2n | = 14. |
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Boechera collinsii |
Boechera serpenticola |
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Phenology | Flowering May–Jun. | Flowering Mar–Jun. |
Habitat | Rocky and gravelly hillsides, prairies, open woods, floodplains | Serpentine ridges and talus |
Elevation | 600-1400 m (2000-4600 ft) | ca. 1100 m (ca. 3600 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 serpenticola has been confused with B. subpinnatifida but is easily distinguished by its entire (versus subpinnatifid to dentate) leaves, shorter (6–8 versus 9–14 mm) petals, and longer (1.5–2 versus 0.5–1 mm) styles. It is known only from Shasta and Trinity counties in north-central California. (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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