Boechera puberula |
Boechera grahamii |
|
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Blue Mountain rockcress, hoary rock-cress, silver rockcress |
Graham's rockcress, Graham's suncress |
|
Habit | Perennials; short-lived; sexual; caudex not woody. | Biennials or perennials; short-lived; apomictic; caudex present or absent. |
Stems | usually 1 per caudex branch, arising from center of rosette near ground surface, (1–)2–6.3 dm, densely pubescent proximally, trichomes short-stalked, 3–8-rayed, 0.1–0.3(–0.5) 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 oblanceolate to linear-oblanceolate, 1.5–5 mm wide, margins usually dentate, not ciliate, surfaces densely pubescent, trichomes short-stalked, 5–12-rayed, 0.05–0.2 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. |
Cauline leaves | 7–45(–65), concealing stem proximally; blade auricles absent or 0.7–3 mm, surfaces of distalmost leaves pubescent. |
(10–)13–52, often concealing stem proximally; blade auricles 1–5 mm, surfaces of distalmost leaves glabrous. |
Racemes | 10–40(–64)-flowered, usually unbranched. |
16–88-flowered, usually unbranched. |
Flowers | ascending to descending at anthesis; sepals pubescent; petals white to lavender, 5–9 × 0.8–1.8 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 | pendent, recurved distal to horizontal to ascending base, 4–10 mm, pubescent, trichomes appressed, branched. |
divaricate-ascending to descending, usually gently curved downward, rarely straight, 5–22(–30) mm, glabrous. |
Fruits | closely pendent, rarely appressed to rachis, sometimes somewhat secund, usually straight, edges parallel, 3–6.5 cm × 1.9–2.2 mm; valves pubescent throughout; ovules 38–64 per ovary; style 0.05–0.1 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, 1.4–1.8 × 1–1.4 mm; wing continuous, 0.1–0.3 mm wide. |
uniseriate to sub-biseriate, 1–1.8 × 0.8–1.2 mm; wing continuous, 0.1–0.25 mm wide. |
2n | = 14. |
= 21. |
Boechera puberula |
Boechera grahamii |
|
Phenology | Flowering Apr–Jul. | Flowering May–Aug. |
Habitat | Ledges, rocky slopes, gravelly hillsides in sagebrush, pinyon-juniper, and mountain shrub communities | Rocky slopes and sandy soil in prairies and open forests |
Elevation | 1300-2900 m (4300-9500 ft) | 100-3200 m (300-10500 ft) |
Distribution |
CA; NV; OR; UT
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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 | Boechera puberula is a diploid species that appears to intergrade with both B. retrofracta and B. subpinnatifida. The glabrous-fruited specimens discussed by R. C. Rollins (1993) represent apomictic hybrids with other species, primarily B. pendulocarpa. (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. 399. | FNA vol. 7, p. 382. |
Parent taxa | Brassicaceae > tribe Boechereae > Boechera | Brassicaceae > tribe Boechereae > Boechera |
Sibling taxa | ||
Synonyms | Arabis puberula, Arabis arida, Arabis beckwithii, Arabis lignipes var. impar, Arabis sabulosa, Arabis subpinnatifida var. beckwithii, Arabis subpinnatifida var. impar, B. beckwithii | 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 | (Nuttall) Dorn: Brittonia, 55: 3. (2003) | (Lehmann) Windham & Al-Shehbaz: Harvard Pap. Bot. 12: 241. (2007) |
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