Boechera howellii |
Boechera breweri |
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Howell's flat-seed rock-cress, Howell's rockcress, pioneer rock-cress |
Brewer's rock-cress |
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Habit | Perennials; long-lived; sexual; caudex usually woody. | Perennials; long-lived; sexual; caudex woody. | ||||
Stems | usually 1 per caudex branch, arising from center of rosette near ground surface, 0.6–2(–3) dm, glabrous throughout. |
usually 1 per caudex branch, arising from center of rosette, somewhat elevated on woody base or from ground surface, 0.6–3.5(–4.5) dm, densely pubescent proximally, trichomes long-stalked and simple, 2-rayed (sometimes all simple), 0.4–1 mm, sparsely pubescent or glabrous distally. |
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Basal leaves | blade narrowly oblanceolate, 1–7 mm wide, margins entire, ciliate proximally, trichomes (simple mixed with a few short-stalked, 2-rayed ones) 0.1–0.4 mm, surfaces glabrous. |
blade oblanceolate, 3–7(–11) mm wide, margins entire or dentate, ciliate proximally, trichomes to 1 mm, surfaces densely pubescent, trichomes long-stalked, 2–4-rayed, 0.4–0.8 mm. |
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Cauline leaves | 2–4, not concealing stem; blade auricles (0–)0.2–1 mm, surfaces of distalmost leaves usually glabrous, rarely ciliate proximally. |
5–15(–28), often concealing stem proximally; blade auricles 0.5–3(–5) mm, surfaces of distalmost leaves pubescent. |
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Racemes | 2–5-flowered, unbranched. |
7–20(–30)-flowered, usually unbranched. |
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Flowers | erect to ascending at anthesis; sepals glabrous; petals white to dark lavender, 4–8 × 1–2.5 mm, glabrous; pollen ellipsoid. |
ascending at anthesis; sepals pubescent; petals usually purple (rarely lavender), 7–12 × 2–4 mm, glabrous; pollen ellipsoid. |
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Fruiting pedicels | ascending, straight, 4–10 mm, glabrous. |
ascending to divaricate-ascending, straight, 3–25 mm, pubescent or glabrous, trichomes spreading, simple and 2-rayed. |
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Fruits | suberect to ascending, usually not appressed to rachis, not secund, straight to curved, edges often somewhat undulate (not parallel), 2.5–6.5 cm × 3–7 mm; valves glabrous; ovules 10–20 per ovary; style 0.05–0.3 mm. |
ascending to divaricate-ascending, not appressed to rachis, not secund, usually curved, rarely straight, edges parallel, 3.5–10 cm × 1.5–2.2 mm; valves usually glabrous, rarely sparsely pubescent; ovules 48–96 per ovary; style 0.05–0.3 mm. |
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Seeds | uniseriate, 3–6 × 2–4 mm; wing continuous, 1.3–2.5 mm wide. |
uniseriate, 1.2–1.7 × 1–1.2 mm; wing continuous, 0.1–0.2 mm wide distally. |
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Boechera howellii |
Boechera breweri |
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Phenology | Flowering Jun–Aug. | |||||
Habitat | Rock outcrops, talus slopes and gravelly soil in alpine and subalpine habitats | |||||
Elevation | 1800-3800 m (5900-12500 ft) | |||||
Distribution |
CA; NV; OR
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CA; OR
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Discussion | Boechera howellii usually is subsumed under B. platysperma, but the two taxa are distinct (see M. D. Windham and I. A. Al-Shehbaz 2006 for detailed comparison). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Subspecies 2 (2 in the flora). Relatively few other sexual diploid species of Boechera co-occur with B. breweri, and the only currently recognized hybrid involving this taxon is B. rubicundula (= B. arcuata × B. breweri; M. D. Windham and I. A. Al-Shehbaz 2007). Boechera breweri appears to be related to B. sparsiflora, and some specimens of subsp. shastaensis can be difficult to separate from that species. The two subspecies appear to intergrade on the western side of the Sacramento Valley from Tehama to Solano counties. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 7, p. 384. | FNA vol. 7, p. 367. | ||||
Parent taxa | ||||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | Arabis howellii, Arabis conferta, Arabis inamoena var. acutata, Arabis platyloba, Arabis platysperma var. howellii, Arabis platysperma var. imparata | Arabis breweri, Arabis breweri var. figularis, Arabis epilobioides | ||||
Name authority | (S. Watson) Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 69. (2006) | (S. Watson) Al-Shehbaz: Novon 13: 384. (2003) | ||||
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