Boechera acutina |
Boechera gunnisoniana |
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point rockcress, sharp-pod rock-cress |
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Habit | Biennials or perennials; short-lived; apomictic; caudex present or absent. | Perennials; usually long-lived; (cespitose); sexual; caudex often woody. |
Stems | usually 1 per caudex branch, arising from center of rosette near ground surface, 1.5–6 dm, densely pubescent proximally, trichomes sessile, 2–4-rayed, 0.15–0.4 mm, usually sparsely pubescent distally, rarely glabrous. |
usually 2–6 per caudex branch, arising from margin of rosette near ground surface, 0.8–2(–2.5) dm, densely pubescent proximally, trichomes short-stalked, 2–4-rayed, 0.08–0.3 mm, mixed with fewer simple ones, usually sparsely pubescent distally, rarely glabrous. |
Basal leaves | blade oblanceolate, 1.5–6 mm wide, margins usually entire, rarely denticulate, ciliate proximally, trichomes (simple), to 0.5 mm, surfaces sparsely to moderately pubescent, trichomes sessile, 3–5 (or 6)-rayed, 0.15–0.35 mm. |
blade linear-oblanceolate, 1–3(–4) mm wide, margins entire, ciliate proximally, trichomes to 0.8 mm, surfaces densely pubescent, trichomes short-stalked, 3–6-rayed, 0.08–0.3 mm. |
Cauline leaves | 2–20(–38), often concealing stem proximally; blade auricles 0.3–2 mm, surfaces of distalmost leaves sparsely pubescent or glabrous. |
3–9, not concealing stem; blade auricles 0.2–1 mm, surfaces of distalmost leaves glabrous or sparsely pubescent. |
Racemes | 5–20(–36)-flowered, usually unbranched. |
7–15-flowered, usually unbranched. |
Flowers | ascending at anthesis; sepals pubescent; petals white or lavender, 5–7 × 0.9–1.3 mm, glabrous; pollen spheroid. |
divaricate-ascending at anthesis; sepals pubescent; petals white or lavender, 4–6 × 1–2 mm, glabrous; pollen ellipsoid. |
Fruiting pedicels | erect to ascending, usually straight, 3–10 mm, pubescent or glabrous, trichomes appressed, branched. |
divaricate, straight or slightly curved, 4–7 mm, glabrous or sparsely pubescent, trichomes appressed, branched. |
Fruits | ascending, not appressed to rachis, not secund, straight, edges parallel, 2.5–7.5 cm × 1.2–1.8 mm; valves glabrous; ovules 46–100 per ovary; style 0.3–1 mm. |
horizontal to divaricate-descending, not appressed to rachis, not secund, straight to slightly curved, edges parallel, 2.5–4 cm × 1–1.5 mm; valves glabrous; ovules 36–54 per ovary; style 0.1–0.2 mm. |
Seeds | uniseriate, 1.8–2.2 × 1–1.4 mm; wing continuous, 0.1–0.4 mm wide. |
uniseriate, 1–1.2 × 0.8–1 mm; wing continuous, 0.1–0.15 mm wide. |
2n | = 14. |
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Boechera acutina |
Boechera gunnisoniana |
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Phenology | Flowering Jun–Jul. | Flowering May–Jun. |
Habitat | Gravelly slopes in meadows, open forests | Rocky slopes and knolls with sagebrush |
Elevation | 1400-1900 m (4600-6200 ft) | 2100-2700 m (6900-8900 ft) |
Distribution |
CA; ID; OR |
CO |
Discussion | Boechera acutina is an apomictic hybrid that clearly contains a genome derived from B. stricta; the other parent remains uncertain. Plants of B. acutina are superficially similar to B. pratincola and are often misidentified as Arabis (Boechera) divaricarpa; the species is easily distinguished from both of those (see M. D. Windham and I. A. Al-Shehbaz 2007b for detailed comparison). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Boechera gunnisoniana is most similar to B. glareosa; it is distinguished from that species by having trichomes smaller (0.08–0.3 versus 0.3–0.6 mm) and more highly divided (mostly 2–4-rayed versus simple and 2-rayed) proximally on stems, and fewer (36–54 versus 50–80) ovules per ovary. The two species are allopatric, with B. glareosa known only from eastern Utah and extreme northwestern Colorado and B. gunnisoniana apparently endemic to Gunnison County in west-central Colorado. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 365. | FNA vol. 7, p. 382. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Arabis acutina, Arabis divaricarpa var. interposita, Arabis drummondii var. interposita, Arabis interposita | Arabis gunnisoniana |
Name authority | (Greene) Windham & Al-Shehbaz: Harvard Pap. Bot. 12: 236. (2007) | (Rollins) W. A. Weber: Phytologia 51: 370. (1982) |
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