Boechera villosa |
Boechera perennans |
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perennial rockcress |
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Habit | Perennials; short-lived; sexual; caudex not woody. | Perennials; long-lived; sexual; caudex woody. |
Stems | 1–3 per caudex branch, arising laterally proximal to sterile shoots near ground surface, ca. 2.5 dm, densely pubescent proximally, trichomes simple and 2-rayed, 0.25–0.7 mm, glabrescent distally. |
usually 2–5 per caudex branch, arising laterally proximal to sterile shoots or rosette, often elevated above ground surface on woody base, (1.5–)2–7 dm, densely pubescent proximally, trichomes short-stalked, Y-shaped, 0.2–0.4 mm, often mixed with 3–5-rayed or (rarely) simple ones, usually glabrous distally. |
Basal leaves | blade oblanceolate to obovate, 2.5–5 mm wide, margins entire, ciliate along petiole, trichomes (simple), to 1 mm, surfaces densely pubescent, trichomes simple and short-stalked, 2- or 3-rayed, 0.25–0.5 mm. |
blade oblanceolate to obovate, 3–15(–20) mm wide, margins dentate, ciliate proximally, trichomes to 1.2 mm, surfaces moderately to densely pubescent, trichomes short-stalked, 3–6-rayed, 0.2–0.4 mm. |
Cauline leaves | 4–6, not concealing stem; blade auricles ca. 1 mm, surfaces of distalmost leaves sparsely pubescent. |
4–12(–17), not concealing stem; blade auricles 0.5–3.5 mm, surfaces of distalmost leaves glabrous. |
Racemes | 6–10-flowered, unbranched. |
16–35-flowered, usually unbranched. |
Flowers | ascending at anthesis; sepals pubescent; petals lavender, 4–5 × 1–1.5 mm, glabrous; pollen ellipsoid. |
ascending at anthesis; sepals pubescent; petals white to purplish, 5–9 × 1–1.5 mm, glabrous or sparsely pubescent (occasionally some trichomes abaxially); pollen ellipsoid. |
Fruiting pedicels | ascending, straight, 6–10 mm, glabrous or sparsely pubescent, trichomes subappressed, branched. |
usually horizontal, straight or slightly recurved, (6–)10–25 mm, usually glabrous. |
Fruits | divaricate-ascending, not appressed to rachis, not secund, slightly curved, edges parallel, 4–5 cm × ca. 1 mm; valves glabrous; ovules ca. 64 per ovary; style ca. 0.2 mm. |
widely pendent, not appressed to rachis, not secund, usually curved, edges parallel, (3–)4–7 cm × 1.7–2.1 mm; valves glabrous; ovules 60–96 per ovary; style 0.05–0.4 mm. |
Seeds | uniseriate, (none mature). |
uniseriate, 1.1–1.5 × 0.9–1.2 mm; wing continuous, 0.1–0.2 mm wide. |
2n | = 14. |
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Boechera villosa |
Boechera perennans |
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Phenology | Flowering May. | Flowering Feb–May. |
Habitat | Basalt outcrop in pinyon-juniper woodlands | Rocky slopes and gravelly soil in warm desert, chaparral, low montane habitats |
Elevation | ca. 2100 m (ca. 6900 ft) | 200-1700 m (700-5600 ft) |
Distribution |
NM |
AZ; CA; NM; NV; TX; UT; Mexico (Baja California, Chihuahua, Sonora)
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Discussion | Boechera villosa is known only from the type collection from the Rio Grande Gorge in Taos County. The holotype was originally identified as Arabis (Boechera) perennans but clearly is more closely related to B. pallidifolia (see M. D. Windham and I. A. Al-Shehbaz 2006 for detailed comparison). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
The circumscription of Boechera perennans followed here is much narrower than that adopted by R. C. Rollins (1993). The most significant difference is the removal of Arabis gracilenta. Recent studies (M. D. Windham and Allphin, in prep.) indicate that the latter represents an older name for the species usually called A. (Boechera) selbyi. Although superficially similar, B. perennans is distinguished from B. gracilenta by having stems arising from above ground surface on woody bases, proximal stems with mostly Y-shaped trichomes, strongly dentate margins on basal leaves, and uniseriate seeds. Typically, B. perennans is a sexual diploid largely restricted to the warm deserts of Arizona, California, Nevada, and southern New Mexico. Plants of B. gracilenta are scattered across the Colorado Plateau (northeast of the range of B. perennans) and are apomictic triploids, apparently produced by hybridization between B. fendleri and B. pallidifolia. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 411. | FNA vol. 7, p. 396. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Arabis perennans, Arabis angulata, Arabis arcuata var. perennans, Arabis eremophila, Arabis recondita | |
Name authority | Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 86. (2006) | (S. Watson) W. A. Weber: Phytologia 51: 370. (1982) |
Web links |