Boechera yorkii |
Boechera fernaldiana |
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last chance rock cress |
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Habit | Perennials; long-lived; sexual; caudex woody. | Perennials; long-lived; (cespitose); sexual; caudex somewhat woody (sometimes with persistent, crowded leaf bases). | ||||
Stems | usually 1 per caudex branch, arising from center of rosette near ground surface, 1–3 dm, densely pubescent proximally, trichomes short-stalked, 4–7-rayed, 0.1–0.5 mm, mixed proximally with simple and short- to long-stalked, 2- or 3-rayed ones, to 1.5 mm, moderately pubescent distally. |
usually 1 per caudex branch, arising from center of rosette, near ground surface or slightly elevated on woody base, 1–3.8 dm, densely pubescent proximally, trichomes short-stalked, 4–8-rayed, 0.04–0.1 mm, sometimes mixed with stalked, 2-rayed ones, to 0.5 mm, usually sparsely pubescent distally. |
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Basal leaves | blade linear-oblanceolate, 1.5–3 mm wide, margins entire, ciliate proximally, trichomes (simple and 2- or 3-rayed), to 1.5 mm, surfaces moderately pubescent, trichomes short-stalked, 4–7-rayed, 0.3–0.6 mm. |
blade narrowly oblanceolate, 1–4 mm wide, margins entire, ciliate along petiole, trichomes (simple), to 1 mm, surfaces densely pubescent, trichomes short-stalked, 4–8-rayed, 0.04–0.1 mm. |
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Cauline leaves | 9–17, concealing stem proximally; blade auricles absent, surfaces of distalmost leaves moderately pubescent. |
5–10, not concealing stem; blade auricles 0.3–2 mm, surfaces of distalmost leaves usually sparsely pubescent. |
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Racemes | 8–35-flowered, usually unbranched. |
10–20-flowered, usually unbranched. |
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Flowers | pendent at anthesis; sepals pubescent; petals yellowish proximally and brick-red distally or, rarely, one color throughout, 9–10 × 0.8–1 mm, glabrous; pollen ellipsoid. |
ascending at anthesis; sepals (purplish or greenish) glabrous or sparsely or moderately pubescent; petals white or purple to lavender, 7–12 × 1.5–4 mm, glabrous; pollen ellipsoid. |
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Fruiting pedicels | reflexed, straight, 1.5–2 mm, pubescent, trichomes appressed, branched. |
divaricate-ascending, straight, 5–20 mm, sparsely pubescent, trichomes appressed, branched. |
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Fruits | (immature) reflexed, often appressed to rachis, not secund, straight, edges parallel, ca. 4 cm; valves pubescent throughout; style ca. 0.3 mm. |
divaricate-ascending, not appressed to rachis, not secund, straight or curved, edges parallel, 3.5–6.5(–7.5) cm × 1–1.6 mm; valves glabrous; ovules 30–72 per ovary; style 0.1–1 mm. |
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Seeds | not seen. |
uniseriate, 1–1.2 × 0.8–1 mm; wing continuous, ca. 0.1 mm wide. |
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Boechera yorkii |
Boechera fernaldiana |
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Phenology | Flowering May. | |||||
Habitat | Crevices and ledges of calcareous rock outcrops | |||||
Elevation | 2200-2400 m (7200-7900 ft) | |||||
Distribution |
CA |
CO; NV; UT |
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Discussion | Boechera yorkii is immediately recognizable by its yellowish to brick-red petals and extremely short (1.5–2 mm), reflexed fruiting pedicels. It is known only from Last Chance Mountains in Inyo County. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Subspecies 2 (2 in the flora). Taxa treated here as subspecies of Boechera fernaldiana share many morphological traits, and most recent authors (R. C. Rollins 1993; N. H. Holmgren 2005b) did not recognize them as distinct. They are consistently separated by the characters listed below, show some degree of molecular divergence (C. D. Bailey et al., unpubl.), and their ranges are separated by ca. 500 km. They clearly represent genetically isolated population systems that warrant taxonomic recognition. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 7, p. 412. | FNA vol. 7, p. 378. | ||||
Parent taxa | ||||||
Sibling taxa | ||||||
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Synonyms | Arabis fernaldiana, Arabis canescens var. stylosa, Arabis fernaldiana var. stylosa | |||||
Name authority | S. Boyd: Madroño 51: 387, figs. 1–3. (2004) | (Rollins) W. A. Weber: Phytologia 51: 370. (1982) | ||||
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