Boechera ultra-alsa |
Boechera repanda |
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Greene's rockcress, Yosemite rockcress |
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Habit | Perennials; long-lived; reproductive mode unknown; caudex woody. | Perennials; short- to long-lived; sexual; caudex usually not 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 1 per caudex branch, arising from center of rosette near ground surface, (1–)2–9 dm, densely pubescent proximally, trichomes short- to long-stalked, 2–6-rayed, 0.2–0.5 mm, rarely mixed with simple ones, to 1.5 mm, glabrous or sparsely pubescent 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 broadly oblanceolate to obovate, 7–25(–50) mm wide, margins usually repand to coarsely dentate, rarely entire, not ciliate, surfaces moderately to densely pubescent, trichomes short- to long-stalked, 3–6-rayed, 0.2–0.5 mm. |
Cauline leaves | 2–5, concealing stem proximally; blade auricles absent, surfaces of distalmost leaves pubescent. |
(3–)8–30, not concealing stem; blade auricles absent, surfaces of distalmost leaves sparsely pubescent. |
Racemes | 3- or 4-flowered, unbranched. |
7–25-flowered, sometimes branched. |
Flowers | not seen. |
erect to ascending at anthesis; sepals glabrous or sparsely pubescent; petals white, 3.5–6 × 0.8–1 mm, glabrous; pollen ellipsoid. |
Fruiting pedicels | erect-ascending, straight, 4–5 mm, glabrous or sparsely pubescent, trichomes appressed, branched. |
erect to divaricate-ascending, straight, 3–10 mm, glabrous or pubescent, trichomes spreading, usually 2–5-rayed, rarely simple. |
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. |
divaricate-ascending, not appressed to rachis, not secund, usually curved, rarely straight, edges parallel, (3.5–)5–13.5 cm × 2.5–4 mm; valves glabrous or pubescent throughout; ovules 34–50 per ovary; style 0.5–1.5 mm. |
Seeds | uniseriate, 5.5–6.5 × 4–4.5 mm; wing continuous, 1–2 mm wide. |
uniseriate, 2.5–5(–6) × 2–3(–3.5) mm; wing continuous, 0.7–1.8 mm wide. |
2n | = 14. |
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Boechera ultra-alsa |
Boechera repanda |
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Phenology | Flowering Jun–Jul. | Flowering Jun–Jul. |
Habitat | Rocky soil | Rock outcrops, talus, and gravelly soil in meadows and open pine forests |
Elevation | ca. 1800 m (ca. 5900 ft) | 1600-3500 m (5200-11500 ft) |
Distribution |
CA |
CA; NV
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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.) |
Boechera repanda is a sexual diploid that is distinguished from all other western North American species by its wide (10–50 mm), repand to coarsely dentate basal leaves. The form recognized as var. greenei appears to be a growth response to ecologically marginal habitats. Boechera repanda occurs sporadically in the Sierra Nevada and Transverse Ranges of California, and barely extends into the Carson Range in western Nevada. Arabis inamoena Greene (1911), not Greene (1908) is an illegitimate name, sometimes found in synonymy with Boechera repanda. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 410. | FNA vol. 7, p. 402. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Arabis repanda, Arabis repanda var. greenei | |
Name authority | Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 86. (2006) | (S. Watson) Al-Shehbaz: Novon 13: 388. (2003) |
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