Boechera williamsii |
Boechera paupercula |
|
---|---|---|
|
boechera paupercula, littleleaf rockcress, small-flower rock-cress, tiny suncress |
|
Habit | Perennials; short-lived; sexual; caudex not woody. | Perennials; long-lived; (cespitose); sexual; caudex often woody. |
Stems | usually 1 per caudex branch, arising from center of rosette near ground surface, 0.7–2.2 dm, glabrous throughout. |
usually 1 per caudex branch, arising from center of rosette near ground surface, 0.3–1.5 dm, densely pubescent proximally, trichomes simple and short-stalked, 2–4-rayed, (0.07–)0.1–0.2 mm, glabrous or sparsely pubescent distally. |
Basal leaves | blade oblanceolate, 1–2 mm wide, margins entire, ciliate near petiole base, trichomes (simple), to 0.4 mm, surfaces sparsely to densely pubescent, trichomes short-stalked, 4–8-rayed, 0.03–0.1 mm. |
blade linear-oblanceolate, 1–3(–5) mm wide, margins entire, ciliate proximally, trichomes to 0.4 mm, surfaces densely pubescent, trichomes short-stalked, 2–6-rayed, (0.07–)0.1–0.2 mm. |
Cauline leaves | 6–11, sometimes concealing stem proximally; blade auricles to 0.5 mm, surfaces of distalmost leaves glabrous. |
2–6, rarely concealing stem; blade auricles 0 (or 0.2–1.5) mm, surfaces of distalmost leaves glabrous. |
Racemes | 5–17-flowered, unbranched. |
3–8-flowered, unbranched. |
Flowers | erect at anthesis; sepals glabrous; petals white, 3–4 × 0.5–0.8 mm, glabrous; pollen ellipsoid. |
erect at anthesis; sepals glabrous or sparsely pubescent; petals lavender to purplish, 4–6(–7) × 1–2 mm, glabrous; pollen ellipsoid. |
Fruiting pedicels | erect, straight, 2–4(–7) mm, glabrous. |
erect, straight, 3–9 mm, glabrous or sparsely pubescent. |
Fruits | erect, usually appressed to rachis, not secund, straight, edges parallel, 2–3.5 cm × 2.2–2.5 mm; valves glabrous; ovules 60–96 per ovary; style 0.05–0.2 mm. |
erect, appressed to rachis, not secund, straight, edges parallel, 2.5–5.5 cm × 1.3–1.7(–2) mm; valves glabrous; ovules 24–40 per ovary; style 0.2–1 mm. |
Seeds | sub-biseriate, 0.7–0.9 × 0.5–0.6 mm, not winged or minutely winged distally. |
usually uniseriate, rarely sub-biseriate, 1.5–2(–2.5) × 1–1.4 mm; wing continuous, 0.3–1 mm wide. |
Boechera williamsii |
Boechera paupercula |
|
Phenology | Flowering May–Jun. | Flowering Jun–Aug. |
Habitat | Gravelly soil in sagebrush-grassland communities | Rock outcrops, talus slopes, gravelly soil in alpine and subalpine habitats |
Elevation | 2300-2800 m (7500-9200 ft) | 2400-3400 m (7900-11200 ft) |
Distribution |
WY |
CA; ID; OR; WA; WY
|
Discussion | Boechera williamsii is distinguished from all other sexual species of the genus by its combination of relatively short (3–4 mm), white petals, minute, 4–8-rayed trichomes on basal leaves, erect, appressed fruits, and relatively small, wingless seeds. It is known only from Fremont and Sublette counties in west-central Wyoming. The taxon traditionally treated as Arabis (Boechera) williamsii var. saximontana is here recognized as an apomictic species of hybrid origin (see M. D. Windham and I. A. Al-Shehbaz 2007b for detailed comparison). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Boechera paupercula is usually subsumed under Arabis (Boechera) lyallii but is amply distinct (see M. D. Windham and I. A. Al-Shehbaz 2006 for detailed comparison). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 411. | FNA vol. 7, p. 394. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Arabis williamsii | Arabis paupercula, Arabis lyallii var. nubigena, Arabis microphylla var. nubigena, Arabis nubigena |
Name authority | (Rollins) Dorn: Vasc. Pl. Wyoming ed. 3, 376. (2001) | (Greene) Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 75. (2006) |
Web links |
|