Boechera puberula |
Boechera duchesnensis |
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Blue Mountain rockcress, hoary rock-cress, silver rockcress |
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Habit | Perennials; short-lived; sexual; caudex not woody. | Perennials; usually long-lived; apomictic; caudex often woody. |
Stems | usually 1 per caudex branch, arising from center of rosette near ground surface, (1–)2–6.3 dm, densely pubescent proximally, trichomes short-stalked, 3–8-rayed, 0.1–0.3(–0.5) mm, similarly pubescent distally. |
usually 1 per caudex branch, arising from center of rosette, elevated on woody base or from near ground surface, 1.5–4.5 dm, densely pubescent proximally, trichomes short-stalked, 2–7-rayed, 0.2–0.5 mm (sometimes mixed with some larger trichomes proximally), sparsely pubescent distally. |
Basal leaves | blade oblanceolate to linear-oblanceolate, 1.5–5 mm wide, margins usually dentate, not ciliate, surfaces densely pubescent, trichomes short-stalked, 5–12-rayed, 0.05–0.2 mm. |
blade linear-oblanceolate, 2–5 mm wide, margins entire or denticulate, ciliate at petiole base, trichomes (simple), to 1 mm, surfaces densely pubescent, trichomes short-stalked, 4–8-rayed, 0.15–0.4 mm. |
Cauline leaves | 7–45(–65), concealing stem proximally; blade auricles absent or 0.7–3 mm, surfaces of distalmost leaves pubescent. |
3–8, not concealing stem; blade auricles 0.7–2 mm, surfaces of distalmost leaves sparsely pubescent. |
Racemes | 10–40(–64)-flowered, usually unbranched. |
11–22-flowered, usually unbranched. |
Flowers | ascending to descending at anthesis; sepals pubescent; petals white to lavender, 5–9 × 0.8–1.8 mm, glabrous; pollen ellipsoid. |
divaricate-ascending at anthesis; sepals pubescent; petals whitish to pale lavender, 7–10 × 1.5–3 mm, glabrous; pollen spheroid. |
Fruiting pedicels | pendent, recurved distal to horizontal to ascending base, 4–10 mm, pubescent, trichomes appressed, branched. |
horizontal, straight or slightly curved, 7–14 mm, pubescent, trichomes appressed, branched. |
Fruits | closely pendent, rarely appressed to rachis, sometimes somewhat secund, usually straight, edges parallel, 3–6.5 cm × 1.9–2.2 mm; valves pubescent throughout; ovules 38–64 per ovary; style 0.05–0.1 mm. |
horizontal, not appressed to rachis, not secund, usually straight, edges parallel, 3.5–5 cm × 1.7–2 mm; valves glabrous proximally, pubescent distally; ovules 72–92 per ovary; style 0.1–0.3 mm. |
Seeds | uniseriate, 1.4–1.8 × 1–1.4 mm; wing continuous, 0.1–0.3 mm wide. |
sub-biseriate, 1.1–1.3 × 0.7–1 mm; wing continuous, ca. 0.1 mm wide. |
2n | = 14. |
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Boechera puberula |
Boechera duchesnensis |
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Phenology | Flowering Apr–Jul. | Flowering May. |
Habitat | Ledges, rocky slopes, gravelly hillsides in sagebrush, pinyon-juniper, and mountain shrub communities | Sandy soil on rocky slopes, mostly in pinyon-juniper woodlands |
Elevation | 1300-2900 m (4300-9500 ft) | 1300-1800 m (4300-5900 ft) |
Distribution |
CA; NV; OR; UT
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CO; NM; UT |
Discussion | Boechera puberula is a diploid species that appears to intergrade with both B. retrofracta and B. subpinnatifida. The glabrous-fruited specimens discussed by R. C. Rollins (1993) represent apomictic hybrids with other species, primarily B. pendulocarpa. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Morphological and isozyme analyses indicate that Boechera duchesnensis is an apomictic species that arose through hybridization between B. formosa and B. pallidifolia (M. D. Windham and Allphin, unpubl.). It is easily distinguished from those species by having fruits that are glabrous proximally and sparsely pubescent distally. It shares this distinctive fruit pubescence with B. xylopoda, an apomictic hybrid between B. perennans and B. pulchra (see Windham and I. A. Al-Shehbaz 2007b for detailed comparison). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 399. | FNA vol. 7, p. 375. |
Parent taxa | Brassicaceae > tribe Boechereae > Boechera | Brassicaceae > tribe Boechereae > Boechera |
Sibling taxa | ||
Synonyms | Arabis puberula, Arabis arida, Arabis beckwithii, Arabis lignipes var. impar, Arabis sabulosa, Arabis subpinnatifida var. beckwithii, Arabis subpinnatifida var. impar, B. beckwithii | Arabis pulchra var. duchesnensis, B. pulchra var. duchesnensis |
Name authority | (Nuttall) Dorn: Brittonia, 55: 3. (2003) | (Rollins) Windham: Harvard Pap. Bot. 12: 239. (2007) |
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