Boechera saximontana

(Rollins) Windham & Al-Shehbaz

Harvard Pap. Bot. 12: 248. 2007

Basionyms: Arabis microphylla var. saximontana Rollins Rhodora 43: 429. 1941
Synonyms: Arabis pendulocarpa var. saximontana (Rollins) Dorn Arabis williamsii var. saximontana (Rollins) Rollins Boechera williamsii var. saximontana (Rollins) Dorn
Treatment appears in FNA Volume 7. Treatment on page 404. Mentioned on page 362.
Perennials; short-lived; apomictic; caudex usually not woody. Stems usually 1 per caudex branch, arising from center of rosette near ground surface, 0.7–3 dm, densely pubescent proximally, trichomes short-stalked, 2–6-rayed, 0.06–0.25 mm, glabrous distally. Basal leaves: blade narrowly oblanceolate, 1–3 mm wide, margins entire, ciliate near petiole base, trichomes (simple and spurred), to 0.4 mm, surfaces sparsely to densely pubescent, trichomes short-stalked, 4–8-rayed, 0.04–0.15 mm. Cauline leaves: 5–9, rarely concealing stem proximally; blade auricles to 0.3–1 mm, surfaces of distalmost leaves glabrous. Racemes 5–13-flowered, usually unbranched. Fruiting pedicels divaricate-ascending, straight, 3–8 mm, glabrous. Flowers ascending at anthesis; sepals pubescent; petals lavender, 4–5 × 0.5–0.8 mm, glabrous; pollen spheroid. Fruits divaricate-ascending, not appressed to rachis, not secund, straight, edges parallel, (2.5–)3–4.7 cm × 1.2–1.7 mm; valves glabrous; ovules 78–112 per ovary; style 0.1–0.5 mm. Seeds uniseriate to sub-biseriate, 1.1–1.4 × 0.7–0.9 mm; wing continuous, 0.05–0.12 mm wide.

Phenology: Flowering Jun–Jul.
Habitat: Rocky soil in sagebrush and open conifer forests
Elevation: 2400-2900 m

Discussion

Boechera saximontana is an apomictic taxon that has been treated as a variety of either Arabis microphylla (R. C. Rollins 1941) or A. (Boechera) williamsii (Rollins 1993; R. D. Dorn 2001). It is easily distinguished from typical collections of those species (see M. D. Windham and I. A. Al-Shehbaz 2007b for detailed comparison), but it is likely that one (or both) were involved in its hybrid origin. It is known from Blaine, Custer, and Lemhi counties in Idaho, and Big Horn and Fremont counties in Wyoming.

References

None.

Lower Taxa

No lower taxa listed.