Boechera saximontana |
Boechera hastatula |
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Hells Canyon rock-cress |
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Habit | Perennials; short-lived; apomictic; caudex usually not woody. | Perennials; short- to long-lived; apomictic or 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. |
1–4 per caudex branch, arising from margin of rosette near ground surface, 1–3 dm, glabrous throughout. |
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 to oblanceolate, 1–3(–5) mm wide, margins entire or minutely toothed, rarely ciliate near petiole base, trichomes (simple), to 0.8 mm, surfaces pubescent or glabrous, trichomes short-stalked, 3–6-rayed, 0.07–0.2 mm. |
Cauline leaves | 5–9, rarely concealing stem proximally; blade auricles to 0.3–1 mm, surfaces of distalmost leaves glabrous. |
4–15, not concealing stem; blade auricles 0.5–2.5 mm, surfaces of distalmost leaves glabrous. |
Racemes | 5–13-flowered, usually unbranched. |
12–40-flowered, usually unbranched. |
Flowers | ascending at anthesis; sepals pubescent; petals lavender, 4–5 × 0.5–0.8 mm, glabrous; pollen spheroid. |
divaricate to pendent at anthesis; sepals pubescent; petals lavender, 5–6 × ca. 1 mm, glabrous; pollen ellipsoid or spheroid. |
Fruiting pedicels | divaricate-ascending, straight, 3–8 mm, glabrous. |
reflexed, abruptly recurved near base, 4–8 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. |
reflexed to closely pendent, usually appressed to rachis, often secund, straight, edges parallel, 0.3–0.42 cm × 1–1.5 mm; valves glabrous; ovules 46–60 per ovary. |
Seeds | uniseriate to sub-biseriate, 1.1–1.4 × 0.7–0.9 mm; wing continuous, 0.05–0.12 mm wide. |
uniseriate, 1–1.3 × 0.8–1 mm; wing continuous, 0.05–0.1 mm wide. |
Boechera saximontana |
Boechera hastatula |
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Phenology | Flowering Jun–Jul. | Flowering Jun–Jul. |
Habitat | Rocky soil in sagebrush and open conifer forests | Igneous rock outcrops |
Elevation | 2400-2900 m (7900-9500 ft) | 1900-2100 m (6200-6900 ft) |
Distribution |
ID; WY |
OR |
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.) |
Of conservation concern. Both sexual and apomictic collections of Boechera hastatula have been identified; further study is needed to determine whether they truly are conspecific. The species is known only from Baker and Wallowa counties. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 404. | FNA vol. 7, p. 383. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Arabis microphylla var. saximontana, Arabis pendulocarpa var. saximontana, Arabis williamsii var. saximontana, B. williamsii var. saximontana | Arabis hastatula |
Name authority | (Rollins) Windham & Al-Shehbaz: Harvard Pap. Bot. 12: 248. (2007) | (Greene) Al-Shehbaz: Novon 13: 386. (2003) |
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