Boechera subpinnatifida |
Boechera horizontalis |
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ashy rock-cress, Klamath rockcress |
Crater Lake rock-cress |
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Habit | Perennials; long-lived; sexual; caudex woody (often with persistent, crowded leaf bases). | Perennials; long-lived; (cespitose); apomictic; caudex woody. |
Stems | usually 1 per caudex branch, arising from center of rosette near ground surface, 1–4(–5) dm, densely pubescent proximally, trichomes short-stalked, 2–6-rayed, 0.1–0.2 mm, sparsely pubescent distally. |
usually 1 per caudex branch, arising from center of rosette, near ground surface or somewhat elevated on woody base, or 1–3.5 dm, sparsely pubescent proximally, trichomes short-stalked, 3–6-rayed, 0.1–0.3 mm, glabrous distally. |
Basal leaves | blade narrowly oblanceolate, 1–4(–5) mm wide, margins prominently dentate to subpinnatifid (leaf margins of sterile shoots often entire), ciliate near petiole base, trichomes (simple or 2-rayed), 0.4–0.6 mm, surfaces densely pubescent, trichomes short-stalked, (2–)4–9-rayed, 0.05–0.2 mm. |
blade narrowly oblanceolate, 1–5 mm wide, margins entire, ciliate near petiole base, trichomes (simple), to 0.4 mm, surfaces densely pubescent, trichomes short-stalked, 3–6-rayed, 0.1–0.3 mm. |
Cauline leaves | (10–)20–60, often concealing stem throughout; blade auricles 0.5–3 mm, surfaces of distalmost leaves moderately to sparsely pubescent. |
3–13, often concealing stem proximally; blade auricles 0.5–1.5 mm, surfaces of distalmost leaves glabrous. |
Racemes | 8–30-flowered, usually unbranched. |
5–32-flowered, usually unbranched. |
Flowers | divaricate-ascending to pendent at anthesis; sepals pubescent; petals usually purple, rarely lavender, 9–14 × 1.5–3 mm, glabrous; pollen ellipsoid. |
divaricate-ascending at anthesis; sepals pubescent; petals lavender to purple, 5–6 × 1.5–2 mm, glabrous; pollen spheroid. |
Fruiting pedicels | reflexed, strongly recurved, 5–15 mm, pubescent, trichomes appressed, branched. |
horizontal to descending, straight or slightly curved downward, 4–11 mm, glabrous. |
Fruits | pendent, not appressed to rachis, not secund, straight to slightly curved, edges parallel, (3.5–)5–8 cm × (1.6–)2–3 mm; valves pubescent throughout; ovules 24–42 per ovary; style 0.5–1 mm. |
horizontal or descending, not appressed to rachis, secund, straight, edges slightly undulate (not parallel), 2–4 cm × 2–3 mm; valves glabrous; ovules 40–54 per ovary; style 0.2–0.5 mm. |
Seeds | uniseriate, 2.5–3.5 × 1.5–2.2 mm; wing continuous or at both ends, 0.4–0.8 mm wide. |
uniseriate, 2–2.5 × 1.7–2 mm; wing continuous, 0.5–1 mm wide. |
2n | = 14. |
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Boechera subpinnatifida |
Boechera horizontalis |
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Phenology | Flowering Mar–May. | Flowering Jul–Aug. |
Habitat | Rock outcrops, talus, gravelly soil, often in sagebrush-grassland communities | Dry pumice slopes |
Elevation | 800-2400 m (2600-7900 ft) | |
Distribution |
CA; ID; NV; OR; UT
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OR |
Discussion | Originally thought to be restricted to northern California and adjacent Oregon, Boechera subpinnatifida is a sexual species that recently has been found in central Idaho, northern Nevada, and northwestern Utah. It appears to intergrade with both B. puberula and B. retrofracta, and species boundaries within this complex need further study. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Morphological evidence suggests that Boechera horizontalis is an apomictic species that arose through hybridization between B. lemmonii and B. suffrutescens (M. D. Windham and I. A. Al-Shehbaz 2007). Boechera horizontalis is known only from the vicinity of Crater Lake in south-central Oregon. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 409. | FNA vol. 7, p. 384. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Arabis subpinnatifida | Arabis horizontalis, Arabis suffrutescens var. horizontalis |
Name authority | (S. Watson) Al-Shehbaz: Novon 13: 389. (2003) | (Greene) Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 266. (2007) |
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