Boechera ultra-alsa |
Boechera pendulina |
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nodding rock cress, rabbit-ear rockcress |
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Habit | Perennials; long-lived; reproductive mode unknown; caudex woody. | Perennials; short- to long-lived; sexual or apomictic; caudex sometimes woody. |
Stems | 1 per caudex branch, arising from center of rosette near ground surface, ca. 1 dm, densely pubescent proximally, trichomes stalked, (2 or) 3–6-rayed, 0.2–0.5 mm, glabrate 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, 4–6 mm wide, margins entire, not ciliate, surfaces moderately pubescent, trichomes long-stalked, 3–6 (or 7)-rayed, 0.2–0.5 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 | 2–5, concealing stem proximally; blade auricles absent, surfaces of distalmost leaves pubescent. |
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 | 3- or 4-flowered, unbranched. |
4–14-flowered, usually unbranched. |
Flowers | not seen. |
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 | erect-ascending, straight, 4–5 mm, glabrous or sparsely pubescent, trichomes appressed, branched. |
divaricate-ascending to horizontal, curved or angled downward, 3–7(–10) mm, usually glabrous, rarely with some simple trichomes. |
Fruits | erect-ascending, sometimes appressed to rachis, not secund, straight, edges parallel, 3–4 cm × ca. 5 mm; valves glabrous; ovules ca. 16 per ovary; style 0.5–0.7 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, 5.5–6.5 × 4–4.5 mm; wing continuous, 1–2 mm wide. |
biseriate, 0.9–1.2 × 0.6–0.9 mm, usually not winged. |
2n | = 14, 21. |
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Boechera ultra-alsa |
Boechera pendulina |
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Phenology | Flowering Jun–Jul. | Flowering Apr–Jun. |
Habitat | Rocky soil | Rock outcrops, open gravelly flats and hillsides in sagebrush, pinyon-juniper, mountain mahogany, open conifer forests |
Elevation | ca. 1800 m (ca. 5900 ft) | 1600-3100 m (5200-10200 ft) |
Distribution |
CA |
AZ; CA; CO; NV; UT; WY
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Discussion | Boechera ultra-alsa is known only from the holotype, from Snow Mountain in Lake County. Originally identified as Arabis (Boechera) platysperma, this specimen differs from that taxon by having petioles without obvious cilia, basal leaves with long-stalked (0.1–0.2 versus less than 0.1 mm) trichomes, and fruits edges parallel (not undulate or constricted between the seeds). (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. 410. | FNA vol. 7, p. 395. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | 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 | Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 86. (2006) | (Greene) W. A. Weber: Phytologia 51: 370. (1982) |
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