Boechera quebecensis |
Boechera shockleyi |
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Shockley's Rock cress |
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Habit | Biennials or perennials; short-lived; apomictic; caudex present or absent. | Perennials; usually short-lived; sexual; caudex not woody, (rarely with persistent, crowded leaf bases). |
Stems | usually 1 per caudex branch, arising from center of rosette near ground surface, 1–4.5 dm, densely pubescent proximally, trichomes sessile, 2–4-rayed, 0.15–0.5 mm, glabrous distally. |
usually 1 per caudex branch, arising from center of rosette near ground surface, (0.8–)2–5 dm, densely pubescent proximally, trichomes short-stalked, 7–12-rayed, 0.1–0.2 mm, densely to sparsely pubescent distally. |
Basal leaves | blade oblanceolate, 5–15 mm wide, margins denticulate, ciliate proximally, trichomes (simple), to 1 mm, surfaces moderately pubescent, trichomes subsessile, (2- or) 3–7-rayed, 0.1–0.3 mm. |
blade oblanceolate, 3–10 mm wide, margins entire, not ciliate, surfaces densely pubescent, trichomes short-stalked, 7–12-rayed, 0.1–0.2 mm. |
Cauline leaves | 4–15, not concealing stem; blade auricles 1–3.5 mm, surfaces of distalmost leaves glabrous. |
14–60, concealing stem for most of length; blade auricles 0.5–4 mm, surfaces of distalmost leaves densely pubescent. |
Racemes | 11–41-flowered, usually unbranched. |
20–70-flowered, usually unbranched. |
Flowers | divaricate at anthesis; sepals pubescent; petals white, 6–7 × 1–2 mm, glabrous; pollen spheroid. |
ascending at anthesis; sepals pubescent; petals lavender, 6–9 × 0.8–1.2 mm, glabrous; pollen ellipsoid. |
Fruiting pedicels | horizontal to slightly descending, curved to straight, 3–8(–14) mm, glabrous or with some subappressed, branched trichomes. |
divaricate-ascending, straight, 7–28 mm, pubescent, trichomes appressed, branched. |
Fruits | horizontal to slightly descending, not appressed to rachis, secund, straight, edges parallel, 3–6 cm × 1.5–2 mm; valves glabrous; ovules 56–94 per ovary. |
divaricate-ascending, not appressed to rachis, not secund, usually curved, rarely straight, edges parallel, 4.5–11 cm × 1.5–2 mm; valves glabrous or sparsely pubescent throughout; ovules 140–190 per ovary; style 0.05–0.6 mm. |
Seeds | uniseriate, 1.2–1.5 × 1–1.3 mm; wing continuous, 0.1–0.15 mm wide. |
sub-biseriate, 1–1.3 × 0.7–0.8 mm; wing distal or, rarely, absent, 0.05–0.1 mm wide. |
Boechera quebecensis |
Boechera shockleyi |
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Phenology | Flowering Jun–Jul. | Flowering Apr–May. |
Habitat | Calcareous rock outcrops and talus slopes | Rock outcrops (primarily dolomite) and gravelly soil in desert scrub, sagebrush, and pinyon-juniper woodlands |
Elevation | 0-300 m (0-1000 ft) | 1200-2200 m (3900-7200 ft) |
Distribution |
QC |
CA; NV; UT
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Discussion | Morphological evidence suggests that Boechera quebecensis is an apomictic species that arose through hybridization between B. holboellii and B. stricta; it is most likely to be confused with B. grahamii (see M. D. Windham and I. A. Al-Shehbaz 2007b for detailed comparison). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Boechera shockleyi is a distinctive sexual species recognizable by the combination of strongly overlapping cauline leaves, a dense covering of minute, 7–12-rayed trichomes, and relatively long, curved, divaricate-ascending fruits with sub-biseriate seeds. It is most similar to B. inyoensis, but differs from that species in its narrower (0.8–1.2 versus 1.2–2 mm) petals, eciliate basal leaves with smaller (0.1–0.2 versus 0.2–0.7 mm) trichomes, greater number (140–190 versus 74–134) of ovules per ovary, and shorter (1–1.3 versus 1.7–2 mm) seeds with distal (versus continuous) wings. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 401. | FNA vol. 7, p. 406. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Arabis divaricarpa var. dechamplainii | Arabis shockleyi |
Name authority | Windham & Al-Shehbaz: Harvard Pap. Bot. 12: 246. (2007) | (Munz) Dorn: Brittonia 55: 3. (2003) |
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