Boechera fructicosa |
Boechera pendulina |
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nodding rock cress, rabbit-ear rockcress |
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Habit | Perennials; short-lived; apomictic; caudex usually not woody. | Perennials; short- to long-lived; sexual or apomictic; caudex sometimes woody. |
Stems | 3 to many per caudex branch, arising from margin of rosette near ground surface, 3.5–6 dm, pubescent proximally, trichomes short-stalked, 2–4-rayed, 0.2–0.3 mm, glabrous distally. |
usually 2–6 per caudex branch, arising from margin of rosette near ground surface, or arising laterally proximal to sterile shoots, 0.6–3(–3.7) dm, sparsely to densely pubescent proximally, trichomes simple, 0.3–0.8 mm, glabrous distally. |
Basal leaves | blade oblanceolate, 3–7 mm wide, margins dentate, ciliate proximally, trichomes (simple), to 0.3 mm, surfaces pubescent, trichomes short-stalked, 4–8-rayed, 0.05–0.2 mm. |
blade oblanceolate to obovate, 1.5–6 mm wide, margins usually entire, rarely dentate, ciliate throughout, trichomes (usually simple), 0.4–1 mm, surfaces pubescent, trichomes simple and short- and long-stalked, 2-rayed, 0.3–0.8 mm. |
Cauline leaves | 5–10, not concealing stem; blade auricles 0.5–1 mm, surfaces of distalmost leaves glabrous. |
2–10(–13), not concealing stem; blade auricles absent or, rarely, to 0.7 mm, surfaces of distalmost leaves glabrous or margins sparsely ciliate. |
Racemes | 10–18-flowered, usually unbranched. |
4–14-flowered, usually unbranched. |
Flowers | divaricate-ascending at anthesis; sepals pubescent; petals lavender, 4–6 × 1–1.5 mm, glabrous; pollen spheroid. |
divaricate-ascending at anthesis; sepals usually sparsely pubescent, rarely glabrous; petals whitish to pale lavender, 4–6 × 1–1.5 mm, glabrous; pollen ellipsoid or spheroid. |
Fruiting pedicels | divaricate-descending, straight, 5–10 mm, glabrous. |
divaricate-ascending to horizontal, curved or angled downward, 3–7(–10) mm, usually glabrous, rarely with some simple trichomes. |
Fruits | divaricate-descending, not appressed to rachis, not secund, curved, edges parallel, 4–6 cm × 1.5–1.8 mm; valves glabrous; ovules 60–70 per ovary; style 0.1–0.4 mm. |
widely pendent, not appressed to rachis, not secund, curved to nearly straight, edges parallel, 2.2–4 cm × 1.2–2.1 mm; valves glabrous; ovules 40–70(–90) per ovary; style 0.1–0.3(–0.5) mm. |
Seeds | uniseriate, 1.5–2 × 1–1.3 mm; wing distal, ca. 0.1 mm wide. |
biseriate, 0.9–1.2 × 0.6–0.9 mm, usually not winged. |
2n | = 14, 21. |
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Boechera fructicosa |
Boechera pendulina |
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Phenology | Flowering Jun–Jul. | Flowering Apr–Jun. |
Habitat | Dry, disturbed soil | Rock outcrops, open gravelly flats and hillsides in sagebrush, pinyon-juniper, mountain mahogany, open conifer forests |
Elevation | ca. 2000 m (ca. 6600 ft) | 1600-3100 m (5200-10200 ft) |
Distribution |
WY |
AZ; CA; CO; NV; UT; WY
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Discussion | Boechera fructicosa is known only from the type collection (A. & E. Nelson 5681) taken near Undine Falls in Park County. Multiple plants are represented (comprising the holotype and four isotypes), though one specimen with the same number at RM is B. stricta. Although the exact parentage of this apomictic hybrid remains in doubt, it is virtually certain that B. microphylla contributed at least one genome. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Although included in Arabis (Boechera) demissa by some authors (e.g., S. L. Welsh et al. 2003; N. H. Holmgren 2005b), B. pendulina is readily distinguished from that species (see M. D. Windham and I. A. Al-Shehbaz 2006 for detailed comparison). Typical collections are sexual diploids, whereas the type of var. russeola is a triploid apomict; further study is needed to determine if the two are conspecific. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 379. | FNA vol. 7, p. 395. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Arabis fructicosa | Arabis pendulina, Arabis demissa var. russeola, Arabis diehlii, Arabis pendulina var. russeola, Arabis setulosa, B. demissa var. pendulina, B. demissa var. russeola, B. pendulina var. russeola |
Name authority | (A. Nelson) Al-Shehbaz: Novon 13: 385. (2003) | (Greene) W. A. Weber: Phytologia 51: 370. (1982) |
Web links |