Boechera breweri |
Boechera grahamii |
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Brewer's rock-cress |
Graham's rockcress, Graham's suncress |
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Habit | Perennials; long-lived; sexual; caudex woody. | Biennials or perennials; short-lived; apomictic; caudex present or absent. | ||||
Stems | usually 1 per caudex branch, arising from center of rosette, somewhat elevated on woody base or from ground surface, 0.6–3.5(–4.5) dm, densely pubescent proximally, trichomes long-stalked and simple, 2-rayed (sometimes all simple), 0.4–1 mm, sparsely pubescent or glabrous distally. |
usually 1 per caudex branch, arising from center of rosette near ground surface, (1.2–)2–12 dm, glabrous or pubescent proximally, trichomes simple and sessile or subsessile, 2 or 3(–6)-rayed, to 1 mm, glabrous distally. |
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Basal leaves | blade oblanceolate, 3–7(–11) mm wide, margins entire or dentate, ciliate proximally, trichomes to 1 mm, surfaces densely pubescent, trichomes long-stalked, 2–4-rayed, 0.4–0.8 mm. |
blade oblanceolate, 1.5–10(–20) mm wide, margins entire or dentate, ciliate proximally, trichomes (simple), to 1 mm, surfaces sparsely to densely pubescent, trichomes sessile or subsessile, 2–4(–7)-rayed, 0.2–0.6 mm. |
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Cauline leaves | 5–15(–28), often concealing stem proximally; blade auricles 0.5–3(–5) mm, surfaces of distalmost leaves pubescent. |
(10–)13–52, often concealing stem proximally; blade auricles 1–5 mm, surfaces of distalmost leaves glabrous. |
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Racemes | 7–20(–30)-flowered, usually unbranched. |
16–88-flowered, usually unbranched. |
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Flowers | ascending at anthesis; sepals pubescent; petals usually purple (rarely lavender), 7–12 × 2–4 mm, glabrous; pollen ellipsoid. |
divaricate at anthesis; sepals glabrous or pubescent; petals usually white, rarely lavender, 5.5–8 × 1–2 mm, glabrous; pollen spheroid. |
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Fruiting pedicels | ascending to divaricate-ascending, straight, 3–25 mm, pubescent or glabrous, trichomes spreading, simple and 2-rayed. |
divaricate-ascending to descending, usually gently curved downward, rarely straight, 5–22(–30) mm, glabrous. |
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Fruits | ascending to divaricate-ascending, not appressed to rachis, not secund, usually curved, rarely straight, edges parallel, 3.5–10 cm × 1.5–2.2 mm; valves usually glabrous, rarely sparsely pubescent; ovules 48–96 per ovary; style 0.05–0.3 mm. |
divaricate-ascending to pendent, not appressed to rachis, not secund, straight or slightly curved, edges parallel, 3.5–9 cm × 1–1.8 mm; valves glabrous; ovules 84–146 per ovary; style 0.05–0.5 mm. |
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Seeds | uniseriate, 1.2–1.7 × 1–1.2 mm; wing continuous, 0.1–0.2 mm wide distally. |
uniseriate to sub-biseriate, 1–1.8 × 0.8–1.2 mm; wing continuous, 0.1–0.25 mm wide. |
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2n | = 21. |
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Boechera breweri |
Boechera grahamii |
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Phenology | Flowering May–Aug. | |||||
Habitat | Rocky slopes and sandy soil in prairies and open forests | |||||
Elevation | 100-3200 m (300-10500 ft) | |||||
Distribution |
CA; OR
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AK; CO; MI; MN; MT; ND; NY; SD; VT; WA; WI; WY; AB; BC; MB; NT; ON; QC; SK; YT
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Discussion | Subspecies 2 (2 in the flora). Relatively few other sexual diploid species of Boechera co-occur with B. breweri, and the only currently recognized hybrid involving this taxon is B. rubicundula (= B. arcuata × B. breweri; M. D. Windham and I. A. Al-Shehbaz 2007). Boechera breweri appears to be related to B. sparsiflora, and some specimens of subsp. shastaensis can be difficult to separate from that species. The two subspecies appear to intergrade on the western side of the Sacramento Valley from Tehama to Solano counties. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Morphological evidence suggests that Boechera grahamii is an apomictic species that arose through hybridization between B. collinsii and B. stricta. Previous authors have assigned these specimens to Arabis (Boechera) divaricarpa (see M. D. Windham and I. A. Al-Shehbaz 2007b for detailed comparison); if these taxa are treated as conspecific, the name B. grahamii has priority. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 7, p. 367. | FNA vol. 7, p. 382. | ||||
Parent taxa | Brassicaceae > tribe Boechereae > Boechera | Brassicaceae > tribe Boechereae > Boechera | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | Arabis breweri, Arabis breweri var. figularis, Arabis epilobioides | Turritis grahamii, Arabis boivinii, Arabis bourgovii, Arabis confinis, Arabis confinis var. brachycarpa, Arabis dacotica, Arabis divaricarpa var. dacotica, Arabis divaricarpa var. hemicylindrica, Arabis divaricarpa var. stenocarpa, Arabis drummondii var. brachycarpa, Arabis holboellii var. brachycarpa, B. brachycarpa, Turritis brachycarpa | ||||
Name authority | (S. Watson) Al-Shehbaz: Novon 13: 384. (2003) | (Lehmann) Windham & Al-Shehbaz: Harvard Pap. Bot. 12: 241. (2007) | ||||
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