Boechera shevockii |
Boechera grahamii |
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Shevock's rockcress |
Graham's rockcress, Graham's suncress |
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Habit | Perennials; long-lived; (pulvinate); sexual; caudex woody (with persistent, crowded leaf bases). | Biennials or perennials; short-lived; apomictic; caudex present or absent. |
Stems | 1 per caudex branch, arising from center of rosette near ground surface, 0.5–1 dm, puberulent proximally, trichomes (scattered), simple, 0.02–0.1 mm, similarly pubescent 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. |
Basal leaves | blade oblong-oblanceolate, 1–2 mm wide, margins entire, ciliate distally, trichomes (simple), 0.02–0.1 mm, surfaces glabrous. |
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. |
Cauline leaves | 3–7, not concealing stem; blade auricles absent, surfaces of distalmost leaves glabrous. |
(10–)13–52, often concealing stem proximally; blade auricles 1–5 mm, surfaces of distalmost leaves glabrous. |
Racemes | 4–7-flowered, unbranched. |
16–88-flowered, usually unbranched. |
Flowers | ascending at anthesis; sepals glabrous; petals lavender, 4–5 × 1–1.2 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. |
Fruiting pedicels | ascending, straight, 5–9 mm, glabrous. |
divaricate-ascending to descending, usually gently curved downward, rarely straight, 5–22(–30) mm, glabrous. |
Fruits | ascending, not appressed to rachis, not secund, straight, edges parallel, 2.5–3 cm × 1–1.5 mm; valves glabrous; ovules 30–34 per ovary; style ca. 0.5 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. |
Seeds | uniseriate, ca. 1.2 × 0.8 mm; wing distal or continuous, ca. 0.1 mm wide. |
uniseriate to sub-biseriate, 1–1.8 × 0.8–1.2 mm; wing continuous, 0.1–0.25 mm wide. |
2n | = 21. |
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Boechera shevockii |
Boechera grahamii |
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Phenology | Flowering Jun. | Flowering May–Aug. |
Habitat | Ledges of rock outcrops | Rocky slopes and sandy soil in prairies and open forests |
Elevation | ca. 2500 m (ca. 8200 ft) | 100-3200 m (300-10500 ft) |
Distribution |
CA |
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 | Boechera shevockii is a close relative of B. davidsonii, from which it is readily distinguished by having puberulent (versus glabrous) stems, shorter (4–5 versus 6–10 mm) petals, and much shorter (5–7 versus 30–80 mm) basal leaves. It is known only from the type specimen, from the southern Sierra Nevada in Tulare County. (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.) |
Source | FNA vol. 7, p. 406. | FNA vol. 7, p. 382. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | 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 | Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 82. (2006) | (Lehmann) Windham & Al-Shehbaz: Harvard Pap. Bot. 12: 241. (2007) |
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