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Rolle's rock-cress

beautiful rockcress, bigfoot hybrid rockcress

Habit Perennials; long-lived; sexual; caudex woody. Perennials; long-lived; apomictic; caudex woody.
Stems

usually 1 per caudex branch, arising from center of rosette, elevated above ground surface on woody base, 1.5–2.5 dm, glabrous throughout.

usually 1 from per caudex branch, arising from center of leaf tuft, elevated above ground surface on woody base, (3–)5–7.5 dm, pubescent proximally, trichomes short-stalked, 2–5-rayed, 0.25–0.9 mm., similarly pubescent distally.

Basal leaves

blade oblanceolate, 3–8 mm wide, margins entire, ciliate proximally, trichomes (simple), 0.2–0.7 mm, surfaces glabrous or sparsely pubescent, trichomes short-stalked, 2–4-rayed, 0.2–0.4 mm.

blade linear-oblanceolate to oblanceolate, 3–7 mm wide, margins entire or somewhat dentate, ciliate near petiole base, trichomes (simple), to 1.5 mm, surfaces densely pubescent, trichomes short-stalked, 4–8-rayed, 0.15–0.5 mm.

Cauline leaves

6–12, sometimes concealing stem proximally;

blade auricles 0.5–2.5 mm, surfaces of distalmost leaves glabrous.

8–18, usually not concealing stem;

blade auricles 1–2 mm, surfaces of distalmost leaves sparsely pubescent.

Racemes

3–7-flowered, unbranched.

20–38-flowered, usually unbranched.

Flowers

divaricate-ascending at anthesis;

sepals glabrous;

petals creamy white, 8–11 × 2–2.5 mm, glabrous;

pollen ellipsoid.

divaricate to pendent at anthesis;

sepals pubescent;

petals purple, 9–12 × 2–3.5 mm, sparsely pubescent (often some trichomes abaxially);

pollen spheroid.

Fruiting pedicels

strongly curved proximally, 4–6 mm, glabrous.

descending-divaricate, usually recurved, 9–20 mm, usually pubescent, rarely glabrous, trichomes subappressed, branched.

Fruits

pendent, not appressed to rachis, not secund, straight to slightly curved, edges undulate (not parallel), 3.5–6 cm × 2.5–3.5 mm;

valves glabrous;

ovules 14–22 per ovary;

style 0.5–1 mm.

reflexed, not appressed to rachis, not secund, straight, edges parallel, 5–7 cm × 2–2.5 mm;

valves glabrous proximally, sparsely pubescent distally;

ovules 98–126 per ovary;

style 0.1–0.5 mm.

Seeds

uniseriate, 3–4 × 1.5–2 mm;

wing distal and proximal, 0.3–0.6 mm wide.

sub-biseriate, 2–2.5 × 1.3–1.6 mm;

wing continuous, 0.2–0.25 mm wide.

Boechera rollei

Boechera xylopoda

Phenology Flowering Aug. Flowering Mar–May.
Habitat Peridotite rocks on sparsely forested slopes Rock outcrops and gravelly slopes, often under shelter of shrubs in desert scrub, sagebrush, and chaparral communities
Elevation 1600-1800 m (5200-5900 ft) 900-2000 m (3000-6600 ft)
Distribution
from FNA
CA
[BONAP county map]
from FNA
CA; NV
[WildflowerSearch map]
[BONAP county map]
Discussion

Boechera rollei is easily distinguished from the habitally similar B. suffrutescens by its longer (8–11 versus 4.5–6 mm) petals, narrower (2.5–3.5 versus 3–6 mm) fruits, and narrower (0.3–0.6 versus 0.8–1.5 mm) seed wings. This distinctive sexual species is known only from the vicinity of the type locality on the divide between the Applegate and Klamath Rivers in Siskiyou County.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Although usually treated as a variety of Arabis (Boechera) pulchra, B. xylopoda is an apomictic taxon that is morphologically intermediate between B. perennans and B. pulchra (see M. D. Windham and I. A. Al-Shehbaz 2007b for detailed comparison) and probably arose through hybridization between those two sexual diploids.

Arabis trichopoda Greene (1908), not Turczaninow (1840) is an illegitimate name, sometimes found in synonymy with Boechera xylopoda.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 7, p. 403. FNA vol. 7, p. 411.
Parent taxa Brassicaceae > tribe Boechereae > Boechera Brassicaceae > tribe Boechereae > Boechera
Sibling taxa
B. acutina, B. arcuata, B. atrorubens, B. bodiensis, B. breweri, B. burkii, B. calderi, B. californica, B. canadensis, B. cascadensis, B. cobrensis, B. collinsii, B. consanguinea, B. constancei, B. covillei, B. crandallii, B. cusickii, B. davidsonii, B. dentata, B. depauperata, B. dispar, B. divaricarpa, B. drepanoloba, B. duchesnensis, B. elkoensis, B. evadens, B. falcatoria, B. falcifructa, B. fecunda, B. fendleri, B. fernaldiana, B. formosa, B. fructicosa, B. glareosa, B. glaucovalvula, B. goodrichii, B. gracilenta, B. gracilipes, B. grahamii, B. gunnisoniana, B. harrisonii, B. hastatula, B. hoffmannii, B. holboellii, B. horizontalis, B. howellii, B. inyoensis, B. johnstonii, B. koehleri, B. laevigata, B. languida, B. lasiocarpa, B. lemmonii, B. lignifera, B. lincolnensis, B. lyallii, B. macounii, B. microphylla, B. missouriensis, B. nevadensis, B. ophira, B. oxylobula, B. paddoensis, B. pallidifolia, B. parishii, B. pauciflora, B. paupercula, B. peirsonii, B. pendulina, B. pendulocarpa, B. perennans, B. perstellata, B. pinetorum, B. pinzliae, B. platysperma, B. polyantha, B. porphyrea, B. pratincola, B. puberula, B. pulchra, B. pusilla, B. pygmaea, B. quebecensis, B. rectissima, B. repanda, B. retrofracta, B. rigidissima, B. rollinsiorum, B. rubicundula, B. saximontana, B. schistacea, B. serotina, B. serpenticola, B. shevockii, B. shockleyi, B. sparsiflora, B. spatifolia, B. stricta, B. subpinnatifida, B. suffrutescens, B. texana, B. tiehmii, B. tularensis, B. ultra-alsa, B. villosa, B. williamsii, B. xylopoda, B. yorkii
B. acutina, B. arcuata, B. atrorubens, B. bodiensis, B. breweri, B. burkii, B. calderi, B. californica, B. canadensis, B. cascadensis, B. cobrensis, B. collinsii, B. consanguinea, B. constancei, B. covillei, B. crandallii, B. cusickii, B. davidsonii, B. dentata, B. depauperata, B. dispar, B. divaricarpa, B. drepanoloba, B. duchesnensis, B. elkoensis, B. evadens, B. falcatoria, B. falcifructa, B. fecunda, B. fendleri, B. fernaldiana, B. formosa, B. fructicosa, B. glareosa, B. glaucovalvula, B. goodrichii, B. gracilenta, B. gracilipes, B. grahamii, B. gunnisoniana, B. harrisonii, B. hastatula, B. hoffmannii, B. holboellii, B. horizontalis, B. howellii, B. inyoensis, B. johnstonii, B. koehleri, B. laevigata, B. languida, B. lasiocarpa, B. lemmonii, B. lignifera, B. lincolnensis, B. lyallii, B. macounii, B. microphylla, B. missouriensis, B. nevadensis, B. ophira, B. oxylobula, B. paddoensis, B. pallidifolia, B. parishii, B. pauciflora, B. paupercula, B. peirsonii, B. pendulina, B. pendulocarpa, B. perennans, B. perstellata, B. pinetorum, B. pinzliae, B. platysperma, B. polyantha, B. porphyrea, B. pratincola, B. puberula, B. pulchra, B. pusilla, B. pygmaea, B. quebecensis, B. rectissima, B. repanda, B. retrofracta, B. rigidissima, B. rollei, B. rollinsiorum, B. rubicundula, B. saximontana, B. schistacea, B. serotina, B. serpenticola, B. shevockii, B. shockleyi, B. sparsiflora, B. spatifolia, B. stricta, B. subpinnatifida, B. suffrutescens, B. texana, B. tiehmii, B. tularensis, B. ultra-alsa, B. villosa, B. williamsii, B. yorkii
Synonyms Arabis rollei Arabis pulchra var. gracilis, Arabis pulchra var. glabrescens, Arabis pulchra var. viridis, B. pulchra var. gracilis
Name authority (Rollins) Al-Shehbaz: Novon 13: 389. (2003) Windham & Al-Shehbaz: Harvard Pap. Bot. 12: 250. (2007)
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