Boechera falcatoria |
Boechera microphylla |
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crevice suncress, little-leaf rockcress, small-flower rockcress, small-leaf rock-cress |
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Habit | Perennials; short- to long-lived; apomictic; caudex sometimes woody. | Perennials; long-lived; (cespitose); sexual or apomictic; caudex woody. |
Stems | usually 2–7 per caudex branch, arising from margin of rosette near ground surface, 0.5–2(–3) dm, densely pubescent proximally, trichomes simple and stalked, 2-rayed, 0.3–0.8 mm, glabrous distally. |
1 or several per caudex branch, arising from center or margin of rosette near ground surface, 0.8–2.8(–3.5) dm, sparsely pubescent proximally, trichomes simple and subsessile, 2-rayed, 0.3–0.6 mm, glabrous distally. |
Basal leaves | blade narrowly oblanceolate, 1–3 mm wide, margins entire, ciliate, trichomes to 1 mm, surfaces pubescent, trichomes stalked, 2–4-rayed, 0.3–0.8 mm. |
blade oblanceolate to linear-oblanceolate, 1–4(–6) mm wide, margins entire or subapically toothed, ciliate proximally, trichomes (simple), to 0.6 mm, surfaces densely pubescent, trichomes short-stalked, 4–8-rayed, 0.05–0.1 mm. |
Cauline leaves | 3–7(–10), not concealing stem; blade auricles 0.2–1 mm, surfaces of distalmost leaves glabrous. |
2–6, not concealing stem; blade auricles 0.5–1.5 mm, surfaces of distalmost leaves glabrous. |
Racemes | 6–15-flowered, unbranched. |
5–17-flowered, usually unbranched. |
Flowers | ascending at anthesis; sepals pubescent; petals white or lavender, 5–7 × 1.5–2.5 mm, glabrous; pollen spheroid. |
ascending at anthesis; sepals glabrous or pubescent; petals lavender to purple, 3.5–5.5 × 1–1.8 mm, glabrous; pollen ellipsoid or spheroid. |
Fruiting pedicels | horizontal to divaricate-ascending, straight, 3–9 mm, glabrous. |
ascending to divaricate-ascending, straight, 4–14 mm, glabrous. |
Fruits | horizontal to divaricate-ascending, not appressed to rachis, not secund, usually strongly curved, edges parallel, 3.5–6.5 cm × 1.7–2 mm; valves glabrous; ovules 50–84 per ovary; style 0.05–0.5 mm. |
ascending to divaricate-ascending, not appressed to rachis, not secund, straight to slightly curved, edges parallel, 3–7 cm × 1–1.5 mm; valves glabrous; ovules 52–72 per ovary; style 0.05–0.3 mm. |
Seeds | uniseriate, 1.5–2 × 1.1–1.5 mm; wing continuous, 0.1–0.2 mm wide. |
uniseriate, 1–1.5 × 0.7–1 mm; wing often distal, ca. 0.1 mm wide. |
2n | = 14, 15. |
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Boechera falcatoria |
Boechera microphylla |
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Phenology | Flowering May–Jun. | Flowering Apr–Jun. |
Habitat | Rock outcrops and gravelly soil in sagebrush and mountain shrub communities | Cliffs and rocky slopes in sagebrush, mountain shrub, and open conifer forests |
Elevation | 2000-2200 m (6600-7200 ft) | 400-2400 m (1300-7900 ft) |
Distribution |
UT |
ID; MT; NV; OR; UT; WA; WY; BC
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Discussion | Of conservation concern. Although the exact parentage of Boechera falcatoria, an apomictic hybrid, remains in doubt, it is virtually certain that B. cusickii contributed at least one genome. Boechera falcatoria has been confused with both B. pendulina and B. perennans, but is amply distinct from both (see M. D. Windham and I. A. Al-Shehbaz 2007 for detailed comparison). Despite the proximity of the type locality to both Idaho and Nevada, the species is known only from northwestern Box Elder County. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Boechera microphylla is recognizable by its minute (0.05–0.1 mm), 4–8-rayed leaf trichomes, mat-forming habit, simple and 2-rayed trichomes on stems proximally, and ascending fruits. Both sexual and apomictic collections are known; further study is needed to determine whether they truly are conspecific. The taxa traditionally treated as Arabis (Boechera) microphylla vars. macounii and thompsonii are here recognized as B. macounii and B. cascadensis, respectively (see M. D. Windham and I. A. Al-Shehbaz 2007 for detailed comparison). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 376. | FNA vol. 7, p. 390. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Arabis falcatoria | Arabis microphylla, Arabis tenuicula |
Name authority | (Rollins) Dorn: Brittonia 55: 3. (2003) | (Nuttall) Dorn: Vasc. Pl. Wyoming ed. 3, 376. (2001) |
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