Draba densifolia |
Draba cruciata |
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dense-leaf Draba, dense-leaf whitlow-grass, Nuttall's Draba, Nuttall's whitlow-grass |
Mineral King Draba |
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Habit | Perennials; (cespitose, pulvinate); caudex branched (dense with persistent leaf remains, branches sometimes terminating in sterile rosettes); scapose. | Perennials; (cespitose, loosely matted); caudex branched (with persistent leaf remains, branches sometimes terminating in sterile rosettes); scapose. |
Stems | unbranched, (0.05–)0.2–1(–1.7) dm, usually glabrous, rarely pubescent, trichomes usually simple, 0.3–0.8 mm, and 2–4 (or 5)-rayed, 0.1–0.6 mm, (rarely predominantly simple ones). |
unbranched, (0.3–)0.5–1.4(–1.8) dm, often glabrous throughout, sometimes pubescent proximally, trichomes stalked, cruciform, 0.07–0.3 mm, with 3–5-rayed ones. |
Basal leaves | rosulate; sessile; blade linear to oblong or oblanceolate-linear, 0.3–0.9(–1.4) cm × 0.5–1.5(–2) mm, margins entire, (ciliate, trichomes simple, 0.3–1.2 mm), surfaces glabrous or sparsely pubescent, abaxially with short-stalked, 2–4-rayed trichomes, 0.1–0.3 mm (midvein prominent), adaxially rarely with subapical, simple trichomes. |
rosulate; petiolate; petiole ciliate throughout; blade oblanceolate to narrowly obovate, (0.4–)0.6–1.1(–1.6) cm × 1.5–3 mm, margins entire or minutely denticulate, surfaces pubescent with stalked, cruciform trichomes, 0.07–0.4 mm, (rarely with fewer, 3–5-rayed ones, sometimes both surfaces glabrous and only margins pubescent, not ciliate, midvein obscure abaxially). |
Cauline leaves | 0. |
0. |
Racemes | 2–10(–22)-flowered, ebracteate, not or slightly elongated in fruit; rachis not or slightly flexuous, glabrous or pubescent as stem. |
(3–)5–18(–22)-flowered, ebracteate, considerably elongated in fruit; rachis not flexuous, glabrous. |
Flowers | sepals ovate, 2–3 mm, usually sparsely pubescent, rarely glabrous, (trichomes simple and short-stalked, 2–4-rayed); petals pale yellow (sometimes fading white), oblanceolate to obovate, 2–5 × 1–1.7(–2) mm; anthers ovate or oblong, 0.4–0.6 mm. |
sepals ovate, 1.5–2 mm, glabrous or pubescent distally, (trichomes short-stalked, 4-rayed); petals yellow, spatulate to oblanceolate, 4–5(–6) × 1.2–2 mm; anthers ovate, 0.4–0.6 mm. |
Fruiting pedicels | divaricate-ascending to ascending (not decurrent basally), straight, (0.7–)1.5–10(–25) mm, usually glabrous, rarely sparsely pubescent, trichomes predominantly simple (0.2–0.7 mm), sometimes 2–4 (or 5)-rayed, (0.1–0.5 mm). |
divaricate-ascending, (not decurrent basally), straight, (4–)5–10(–13) mm, glabrous. |
Fruits | ovoid or ovate-lanceolate, plane (not curved), flattened, (2.5–)3–6(–8) × 2–3 mm; valves pubescent or puberulent, trichomes simple and short-stalked, 2–5-rayed, 0.1–0.4 mm; ovules 4–12 per ovary; style 0.3–0.6(–1) mm. |
narrowly lanceolate to elliptic-lanceolate, plane (not curved), flattened, (4–)6–12(–16) × 1.5–3 mm; valves glabrous or puberulent, trichomes simple and short stalked, 2–4-rayed, 0.03–0.15 mm; ovules 6–10(–12) per ovary; style (0.1–)0.3–0.8 mm. |
Seeds | oblong to ovoid, 1.2–2(–2.6) × 0.9–1.2(–1.4) mm. |
ovoid, 1–1.7 × 0.8–1.3 mm. |
2n | = 36. |
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Draba densifolia |
Draba cruciata |
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Phenology | Flowering Jun–Aug. | Flowering Jul–Aug. |
Habitat | Rock outcrops and talus, rocky knolls, alpine ridges | Subalpine areas, ridges in pine and fir forests |
Elevation | 800-3700 m (2600-12100 ft) | 2500-3100 m (8200-10200 ft) |
Distribution |
AK; CA; ID; NV; OR; UT; WA; WY; AB; BC
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CA |
Discussion | Draba densifolia is one of the most highly variable North American members of the genus, as evidenced by the extensive synonymy. The species is an apomict (G. A. Mulligan 1976) and it occupies tremendous geographic, edaphic, and altitudinal ranges. In forms corresponding to the type of D. sphaerula, the flowering stems are 2-flowered, and the stems, leaves, and fruiting pedicels are to 5, 1.5, and 0.6 mm, respectively. By contrast, forms comparable to the type of D. caeruleomontana var. piperi have stems, leaves, and fruiting pedicels to 17, 1.3, and 2.5 cm, respectively. Between these remarkable extremes fall all of the other populations of the species. Draba densifolia is sometimes confused with D. paysonii, which it resembles, in being a cespitose, scapose, and densely pulvinate perennial having narrowly linear or oblong to linear-oblanceolate leaf blades with strongly ciliate margins. It is easily distinguished from the latter by having glabrous adaxial leaf blade surfaces, only sparsely pubescent abaxial surfaces, and often glabrous fruiting pedicels and rachises. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Of conservation concern. Draba cruciata is known only from the Sierra Nevada of Tulare County. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 306. | FNA vol. 7, p. 303. |
Parent taxa | Brassicaceae > tribe Arabideae > Draba | Brassicaceae > tribe Arabideae > Draba |
Sibling taxa | ||
Synonyms | D. caeruleomontana, D. caeruleomontana var. piperi, D. glacialis var. pectinata, D. globosa var. sphaerula, D. mulfordiae, D. nelsonii, D. oligosperma var. pectinata, D. pectinata, D. sphaerula | |
Name authority | Nuttall: in J. Torrey and A. Gray, Fl. N. Amer. 1: 104. (1838) | Payson: Amer. J. Bot. 4: 265. (1917) |
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