Boechera saximontana |
Boechera gracilenta |
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Selby's rockcress |
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Habit | Perennials; short-lived; apomictic; caudex usually not woody. | Perennials; short- or (rarely) long-lived; apomictic; caudex usually not woody. |
Stems | usually 1 per caudex branch, arising from center of rosette near ground surface, 0.7–3 dm, densely pubescent proximally, trichomes short-stalked, 2–6-rayed, 0.06–0.25 mm, glabrous distally. |
1–9 per caudex branch, arising from center or margin of rosette near ground surface, (1.5–)2.5–5.5 dm, densely pubescent proximally, trichomes short-stalked, 2–4-rayed, 0.1–0.5 mm, mixed with some simple ones, to 0.8 mm, glabrous distally. |
Basal leaves | blade narrowly oblanceolate, 1–3 mm wide, margins entire, ciliate near petiole base, trichomes (simple and spurred), to 0.4 mm, surfaces sparsely to densely pubescent, trichomes short-stalked, 4–8-rayed, 0.04–0.15 mm. |
blade oblanceolate, 2–9 mm wide, margins shallowly dentate or sometimes entire, ciliate proximally, trichomes (simple and spurred), to 1.2 mm, surfaces moderately to densely pubescent, trichomes short-stalked, 4–6(–8)-rayed, 0.1–0.5 mm. |
Cauline leaves | 5–9, rarely concealing stem proximally; blade auricles to 0.3–1 mm, surfaces of distalmost leaves glabrous. |
4–9, not concealing stem; blade auricles 1–3 mm, surfaces of distalmost leaves usually glabrous. |
Racemes | 5–13-flowered, usually unbranched. |
7–20-flowered, usually unbranched. |
Flowers | ascending at anthesis; sepals pubescent; petals lavender, 4–5 × 0.5–0.8 mm, glabrous; pollen spheroid. |
ascending at anthesis; sepals pubescent; petals lavender, 6–7 × 1.5–2 mm, glabrous; pollen spheroid. |
Fruiting pedicels | divaricate-ascending, straight, 3–8 mm, glabrous. |
divaricate-ascending, gently curved downward, (7–)10–18 mm, glabrous. |
Fruits | divaricate-ascending, not appressed to rachis, not secund, straight, edges parallel, (2.5–)3–4.7 cm × 1.2–1.7 mm; valves glabrous; ovules 78–112 per ovary; style 0.1–0.5 mm. |
usually widely pendent, rarely horizontal, not appressed to rachis, not secund, slightly curved, edges parallel, (3–)4.5–7 cm × 1.7–2 mm; valves glabrous; ovules 60–96 per ovary; style 0.1–0.3 mm. |
Seeds | uniseriate to sub-biseriate, 1.1–1.4 × 0.7–0.9 mm; wing continuous, 0.05–0.12 mm wide. |
sub-biseriate, 1.2–1.8 × 0.9–1.2 mm; wing continuous, 0.1–0.25 mm wide. |
Boechera saximontana |
Boechera gracilenta |
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Phenology | Flowering Jun–Jul. | Flowering Apr–May. |
Habitat | Rocky soil in sagebrush and open conifer forests | Rocky slopes and sandy soil in pinyon-juniper woodlands and mountain shrub communities |
Elevation | 2400-2900 m (7900-9500 ft) | 1900-2300 m (6200-7500 ft) |
Distribution |
ID; WY |
AZ; CO; NM; UT
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Discussion | Boechera saximontana is an apomictic taxon that has been treated as a variety of either Arabis microphylla (R. C. Rollins 1941) or A. (Boechera) williamsii (Rollins 1993; R. D. Dorn 2001). It is easily distinguished from typical collections of those species (see M. D. Windham and I. A. Al-Shehbaz 2007b for detailed comparison), but it is likely that one (or both) were involved in its hybrid origin. It is known from Blaine, Custer, and Lemhi counties in Idaho, and Big Horn and Fremont counties in Wyoming. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Morphological evidence suggests that Boechera gracilenta is an apomictic species that arose through hybridization between B. fendleri and B. pallidifolia; it is superficially similar to the sexual diploid B. perennans but is not closely related (see M. D. 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. 404. | FNA vol. 7, p. 381. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Arabis microphylla var. saximontana, Arabis pendulocarpa var. saximontana, Arabis williamsii var. saximontana, B. williamsii var. saximontana | Arabis gracilenta, Arabis selbyi, B. selbyi |
Name authority | (Rollins) Windham & Al-Shehbaz: Harvard Pap. Bot. 12: 248. (2007) | (Greene) Windham & Al-Shehbaz: Harvard Pap. Bot. 12: 240. (2007) |
Web links |