Boechera yorkii |
Boechera fructicosa |
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last chance rock cress |
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Habit | Perennials; long-lived; sexual; caudex woody. | Perennials; short-lived; apomictic; caudex usually not woody. |
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. |
3 to many per caudex branch, arising from margin of rosette near ground surface, 3.5–6 dm, pubescent proximally, trichomes short-stalked, 2–4-rayed, 0.2–0.3 mm, glabrous distally. |
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 oblanceolate, 3–7 mm wide, margins dentate, ciliate proximally, trichomes (simple), to 0.3 mm, surfaces pubescent, trichomes short-stalked, 4–8-rayed, 0.05–0.2 mm. |
Cauline leaves | 9–17, concealing stem proximally; blade auricles absent, surfaces of distalmost leaves moderately pubescent. |
5–10, not concealing stem; blade auricles 0.5–1 mm, surfaces of distalmost leaves glabrous. |
Racemes | 8–35-flowered, usually unbranched. |
10–18-flowered, usually unbranched. |
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. |
divaricate-ascending at anthesis; sepals pubescent; petals lavender, 4–6 × 1–1.5 mm, glabrous; pollen spheroid. |
Fruiting pedicels | reflexed, straight, 1.5–2 mm, pubescent, trichomes appressed, branched. |
divaricate-descending, straight, 5–10 mm, glabrous. |
Fruits | (immature) reflexed, often appressed to rachis, not secund, straight, edges parallel, ca. 4 cm; valves pubescent throughout; style ca. 0.3 mm. |
divaricate-descending, not appressed to rachis, not secund, curved, edges parallel, 4–6 cm × 1.5–1.8 mm; valves glabrous; ovules 60–70 per ovary; style 0.1–0.4 mm. |
Seeds | not seen. |
uniseriate, 1.5–2 × 1–1.3 mm; wing distal, ca. 0.1 mm wide. |
Boechera yorkii |
Boechera fructicosa |
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Phenology | Flowering May. | Flowering Jun–Jul. |
Habitat | Crevices and ledges of calcareous rock outcrops | Dry, disturbed soil |
Elevation | 2200-2400 m (7200-7900 ft) | ca. 2000 m (ca. 6600 ft) |
Distribution |
CA |
WY |
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.) |
Boechera fructicosa is known only from the type collection (A. & E. Nelson 5681) taken near Undine Falls in Park County. Multiple plants are represented (comprising the holotype and four isotypes), though one specimen with the same number at RM is B. stricta. Although the exact parentage of this apomictic hybrid remains in doubt, it is virtually certain that B. microphylla contributed at least one genome. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 412. | FNA vol. 7, p. 379. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Arabis fructicosa | |
Name authority | S. Boyd: Madroño 51: 387, figs. 1–3. (2004) | (A. Nelson) Al-Shehbaz: Novon 13: 385. (2003) |
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