Draba ruaxes |
Draba arida |
|
---|---|---|
coast mountain Draba, coast mountain whitlow-grass, coast mountain whitlow-grass Draba, Rainier Draba |
desert Draba |
|
Habit | Perennials; (cespitose, forming tufts); caudex branched (with persistent leaf bases, branches some terminating in sterile rosettes); scapose. | Perennials; (cespitose); caudex branched (with persistent leaf remains, branches relatively short); not scapose. |
Stems | unbranched, 0.2–0.6(–0.8) dm, often pubescent throughout, sometimes glabrate distally, trichomes simple, 0.4–1 mm, and 2–4-rayed, 0.1–0.4 mm. |
usually unbranched, (0.3–)0.4–1 dm, pubescent throughout, trichomes simple and 2-rayed, 0.4–1.4 mm, and shorter, 2–4-rayed ones, 0.05–0.3 mm. |
Basal leaves | rosulate; subsessile; petiole base and margin ciliate, (trichomes simple, 0.4–1.4 mm); blade oblanceolate to obovate or suborbicular, 0.3–1 cm × 2–4.5 mm, margins entire, surfaces pubescent, abaxially with stalked, 2–10-rayed, stellate trichomes, 0.2–0.8 mm, adaxially with simple trichomes, 0.4–1 mm, sometimes with smaller, 2–4-rayed ones, (midvein obscure). |
rosulate; subsessile; petiole not ciliate; blade obovate to spatulate or oblanceolate, 0.6–1.9(–2.4) cm × 2–5(–8) mm, (base ciliate, trichomes simple and 2-rayed), margins entire, surfaces abaxially pubescent with stalked, (2–)4-rayed trichomes, 0.3–0.6 mm, adaxially with simple and stalked, 2-rayed trichomes, 0.3–0.6 mm, and smaller, 3- or 4-rayed ones. |
Cauline leaves | 0. |
(1 or) 2–5; sessile; blade oblong to oblanceolate or ovate, margins entire, surfaces pubescent as basal. |
Racemes | (2–)4–10(–14)-flowered, ebracteate, elongated in fruit; rachis not flexuous, pubescent as stem or glabrous. |
12–40-flowered, ebracteate, slightly elongated in fruit; rachis not flexuous, pubescent, trichomes simple and 2–4-rayed. |
Flowers | sepals ovate, 2–3 mm, pubescent, (trichomes simple with fewer, 2-rayed ones); petals bright yellow, obovate, 4–6 × 2–3.5 mm; anthers oblong, 0.4–0.5 mm. |
sepals broadly ovate, 2–2.7 mm, pubescent, (trichomes simple and short-stalked, 2–4-rayed); petals yellow, spatulate to oblanceolate, 3.5–5 × 1.4–2 mm; anthers oblong, 0.4–0.6 mm. |
Fruiting pedicels | ascending to divaricate-ascending, straight or slightly curved upward, 3–7(–9) mm, pubescent or glabrous, trichomes simple and 2–4-rayed. |
horizontal to divaricate-ascending, straight, (3–)4–8 mm, pubescent, trichomes simple and 2–4-rayed (0.1–0.5 mm). |
Fruits | elliptic to lanceolate or ovate to suborbicular, plane, flattened, 4–8(–10) × 3–4.5 mm; valves puberulent, trichomes simple with fewer 2-rayed ones, 0.1–0.35 mm; ovules 12–16 per ovary; style 0.5–0.9(–1.1) mm. |
elliptic or ovate to lanceolate, plane, slightly inflated basally, 4–7 × 2.5–3.5 mm; valves pubescent, trichomes simple and stalked, 2–4-rayed, 0.05–0.4 mm; ovules 8–12 per ovary; style 0.5–1.2(–1.4) mm. |
Seeds | oblong, 1.5–2 × 1–1.3 mm. |
ovoid, 1–1.4 × 0.6–0.8 mm. |
2n | = 72. |
= 24. |
Draba ruaxes |
Draba arida |
|
Phenology | Flowering Jun–Jul. | Flowering May–Jul. |
Habitat | Rock outcrops, talus slopes, ridges, alpine summits | Rock crevices and gravelly soil in conifer and subalpine shrub communities |
Elevation | 500-2400 m (1600-7900 ft) | 2100-3400 m (6900-11200 ft) |
Distribution |
AK; WA; AB; BC; YT
|
NV |
Discussion | C. L. Hitchcock (1941) treated Draba ruaxes as a variety of D. ventosa; as demonstrated by G. A. Mulligan (1971b), the two are quite distinct. Draba ruaxes is an outcrossing hexaploid with well-formed anthers and pollen, and abundant, simple trichomes on leaves, stems, sepals, and fruits. By contrast, D. ventosa is an apomictic triploid with abortive anthers and/or pollen, and no simple trichomes anywhere on the plant. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Of conservation concern. Draba arida is a sexually reproducing, diploid member of the D. ventosa complex that may have been involved in the origin of the more widespread apomictic triploids (M. A. Beilstein and M. D. Windham 2003). The species is known from the Monitor, Toiyabe, and Toquima ranges in Lander and Nye counties. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 334. | FNA vol. 7, p. 292. |
Parent taxa | Brassicaceae > tribe Arabideae > Draba | Brassicaceae > tribe Arabideae > Draba |
Sibling taxa | ||
Synonyms | D. ventosa var. ruaxes | |
Name authority | Payson & H. St. John: Proc. Biol. Soc. Wash. 43: 117. (1930) | C. L. Hitchcock: Revis. Drabas W. N. Amer., 52, plate 3, fig. 23. (1941) |
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