Boechera collinsii |
Boechera bodiensis |
|
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collin's suncress, Collins' rockcress |
Bodie Hills rock cress |
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Habit | Perennials; usually short-lived; sexual; caudex not woody. | Perennials; long-lived; (cespitose); apomictic; caudex somewhat 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, 1.5–3.5 dm, densely pubescent proximally, trichomes short-stalked, 5–10-rayed, to 0.7 mm, sparsely pubescent or 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 to 0.7 mm, surfaces densely pubescent, trichomes short-stalked, 5–10-rayed, 0.08–0.25 mm. |
Cauline leaves | (8–)15–40, concealing stem proximally; blade auricles 1–3 mm, surfaces of distalmost leaves usually sparsely pubescent. |
4–9, not concealing stem; blade auricles 0.5–2 mm, surfaces of distalmost leaves pubescent. |
Racemes | (15–)30–90-flowered, usually unbranched. |
8–25-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 lavender to purple, 4–5 × ca. 1 mm, glabrous; pollen spheroid. |
Fruiting pedicels | reflexed, abruptly recurved at base, otherwise straight, 4–13 mm, glabrous or sparsely pubescent, trichomes usually simple. |
ascending to divaricate-ascending, 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. |
divaricate-ascending, not appressed to rachis, not secund, straight or curved, edges parallel, 4–6.2 cm × 1.2–1.8 mm; valves glabrous; ovules 48–68 per ovary; style 0.1–0.2 mm. |
Seeds | uniseriate, 1–1.4 × 0.8–1 mm; wing continuous (rarely absent), to 0.1 mm wide. |
uniseriate, 1–1.5 × 0.8–1.2 mm; wing continuous, 0.1–0.15 mm wide. |
2n | = 14. |
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Boechera collinsii |
Boechera bodiensis |
|
Phenology | Flowering May–Jun. | Flowering Jul–Aug. |
Habitat | Rocky and gravelly hillsides, prairies, open woods, floodplains | Loose soil, crevices of igneous rock |
Elevation | 600-1400 m (2000-4600 ft) | 2400-2900 m (7900-9500 ft) |
Distribution |
ID; MN; MT; ND; NE; SD; WY; AB; MB; QC; SK
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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.) |
Of conservation concern. In his original description, Rollins suggested that Boechera bodiensis is closely related to B. cobrensis and B. falcifructa. Subsequent studies (M. D. Windham and I. A. Al-Shehbaz, unpubl.) indicate that both B. bodiensis and B. falcifructa are apomictic hybrids containing one or more genomes derived from B. cobrensis. In the case of B. falcifructa, the second parent is clearly B. fernaldiana, but the second parent of B. bodiensis remains uncertain. Boechera bodiensis is most similar to B. falcifructa. The latter differs by having gently recurved fruiting pedicels 6–12 mm, 62–80 ovules per ovary, and pendulous fruits; it is known from Elko and Lander counties, Nevada. By contrast, B. bodiensis has straight fruiting pedicels 3–7 mm long, divaricate-ascending fruits, 48–68 ovules per ovary, and is known from Mono County, California, and Lyon and Mineral counties, Nevada. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 370. | FNA vol. 7, p. 367. |
Parent taxa | Brassicaceae > tribe Boechereae > Boechera | Brassicaceae > tribe Boechereae > Boechera |
Sibling taxa | ||
Synonyms | Arabis collinsii, Arabis holboellii var. collinsii, Arabis retrofracta var. collinsii | Arabis bodiensis |
Name authority | (Fernald) Á. Löve & D. Löve: Taxon 31: 125. (1982) | (Rollins) Al-Shehbaz: Novon 13: 384. (2003) |
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