Boechera macounii

(S. Watson) Windham & Al-Shehbaz

Harvard Pap. Bot. 11: 267. 2007.

Basionym: Arabis macounii S. Watson Proc. Amer. Acad. Arts 26: 124. 1891
Synonyms: Arabis densicaulis A. Nelson Arabis microphylla var. macounii (S. Watson) Rollins
Treatment appears in FNA Volume 7. Treatment on page 389. Mentioned on page 357, 364, 380, 390.

Perennials; usually long-lived; apomictic; caudex often woody. Stems 1 or several per caudex branch, arising from center or margin of rosette near ground surface, 2–3.6 dm, densely pubescent proximally, trichomes simple and short-stalked, 2-rayed, 0.1–0.8 mm, glabrous distally. Basal leaves: blade oblanceolate to linear-oblanceolate, 1–3(–5) mm wide, margins entire or minutely toothed, ciliate proximally, trichomes (simple), to 0.7 mm, surfaces densely pubescent, trichomes short-stalked, 3–6-rayed, 0.07–0.3 mm. Cauline leaves: (5–)9–16, often concealing stem proximally; blade auricles 0.5–1.5 mm, surfaces of distalmost leaves glabrous. Racemes 10–33-flowered, usually unbranched. Fruiting pedicels divaricate-ascending to horizontal, straight, 5–13(–17) mm, usually densely pubescent, rarely glabrous, trichomes appressed, 2- or 3-rayed. Flowers divaricate-ascending at anthesis; sepals pubescent; petals lavender to purple, 4–5 × 0.5–0.8 mm, glabrous; pollen spheroid. Fruits divaricate-ascending to descending, not appressed to rachis, not secund, usually curved, edges parallel, 3.5–6.5 cm × 0.8–1.2 mm; valves glabrous; ovules 56–78 per ovary; style 0.1–0.4 mm. Seeds uniseriate, 1–1.2 × 0.7–1 mm; wing often continuous, 0.05–0.15 mm wide.

Phenology: Flowering May–Jul.
Habitat: Rocky hillsides in open pinewoods
Elevation: 2200-2900 m


Morphological evidence suggests that Boechera macounii is an apomictic species that arose through hybridization between B. collinsii and B. microphylla (see M. D. Windham and I. A. Al-Shehbaz 2007 for detailed comparison).

Selected References


Lower Taxa

... more about "Boechera macounii"
Ihsan A. Al-Shehbaz +  and Michael D. Windham +
(S. Watson) Windham & Al-Shehbaz +
Arabis macounii +
B.C. +, Idaho +, Mont. +  and Wyo. +
2200-2900 m +
Rocky hillsides in open pinewoods +
Flowering May–Jul. +
Harvard Pap. Bot. +
Arabis densicaulis +  and Arabis microphylla var. macounii +
Boechera macounii +
Boechera +
species +