Boechera saximontana |
Boechera dispar |
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pinyon rock cress |
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Habit | Perennials; short-lived; apomictic; caudex usually not woody. | Perennials; usually long-lived; sexual; caudex often 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. |
usually 1 per caudex branch, arising from center of rosette near ground surface, 0.9–3 dm, densely pubescent proximally, trichomes short-stalked, 5–12-rayed, 0.1–0.3 mm, sparsely pubescent to glabrescent 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 linear-oblanceolate, 2–5 mm wide, margins entire, not ciliate, surfaces densely pubescent, trichomes short-stalked, 5–12(–16)-rayed, 0.1–0.3 mm. |
Cauline leaves | 5–9, rarely concealing stem proximally; blade auricles to 0.3–1 mm, surfaces of distalmost leaves glabrous. |
1–5, not concealing stem; blade without auricles, surfaces of distalmost leaves pubescent. |
Racemes | 5–13-flowered, usually unbranched. |
4–15(–20)-flowered, 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 purple to lavender, 3.5–6 × 1–1.5 mm, glabrous; pollen ellipsoid. |
Fruiting pedicels | divaricate-ascending, straight, 3–8 mm, glabrous. |
ascending, straight, 4–15(–25) mm, pubescent, trichomes appressed, branched. |
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. |
divaricate-ascending, not appressed to rachis, not secund, straight, edges parallel, 4–7.3 cm × 2.7–4 mm; valves glabrous; ovules 44–52 per ovary; style 0.05–0.1 mm. |
Seeds | uniseriate to sub-biseriate, 1.1–1.4 × 0.7–0.9 mm; wing continuous, 0.05–0.12 mm wide. |
uniseriate, 1.9–2.3 mm in diam.; wing continuous, 0.3–0.5 mm wide. |
Boechera saximontana |
Boechera dispar |
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Phenology | Flowering Jun–Jul. | Flowering Apr–May. |
Habitat | Rocky soil in sagebrush and open conifer forests | Rocky slopes and gravelly soil in desert scrub and pinyon-juniper communities |
Elevation | 2400-2900 m (7900-9500 ft) | 1500-2300 m (4900-7500 ft) |
Distribution |
ID; WY |
CA; NV |
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.) |
Boechera dispar is a distinctive sexual diploid that is known from Inyo, Mono, and San Bernardino counties, California, and Nye County, Nevada. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 404. | FNA vol. 7, p. 374. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Arabis microphylla var. saximontana, Arabis pendulocarpa var. saximontana, Arabis williamsii var. saximontana, B. williamsii var. saximontana | Arabis dispar, Arabis juniperina, Arabis nardina, Arabis salubris |
Name authority | (Rollins) Windham & Al-Shehbaz: Harvard Pap. Bot. 12: 248. (2007) | (M. E. Jones) Al-Shehbaz: Novon 13: 384. (2003) |
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