Draba sibirica |
Draba incerta |
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Siberian whitlowgrass |
whitlow-wort, Yellowstone Draba, Yellowstone Draba whitlow-wort, Yellowstone whitlow-grass, Yellowstone whitlow-wort |
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Habit | Perennials; (stoloniferous); caudex branched (sparsely covered with persistent petiole remains, branches slender, creeping); scapose. | Perennials; (cespitose, often pulvinate); caudex branched (dense with persistent leaf remains, branches sometimes terminating in sterile rosettes); scapose. |
Stems | (subdecumbent when sterile), unbranched, 0.5–2.5 dm, sparsely to densely hispid, trichomes malpighiaceous, (flowering scapes sparsely pilose proximally with simple trichomes, often glabrous on distal 1/2). |
unbranched, (0.2–)0.4–1.4(–2.1) dm, often pubescent throughout, sometimes glabrous distally, trichomes often simple and 2–5-rayed, 0.1–0.5 mm, (sometimes with mostly subpectinate ones). |
Basal leaves | rosulate; petiolate; blade oblong-lanceolate or oblanceolate, 0.4–2.2 cm × 1–5(–10) mm, margins entire, surfaces often pubescent, sometimes glabrous (except margins), with appressed, malpighiaceous trichomes (these sometimes with 1 or 2 shorter, lateral branches, appearing 3-fid or cross-shaped). |
rosulate; petiolate; petiole (0–1 cm), ciliate throughout; blade narrowly oblanceolate to linear, (0.4–)0.6–1.7(–2.5) cm × (1–)1.5–3.5(–5) mm, margins entire, (ciliate, trichomes usually simple, rarely 2-rayed, 0.2–1.1 mm), surfaces usually pubescent with short-stalked, pectinate trichomes, 0.15–0.5 mm, sometimes also with 4–6-rayed ones, (midvein usually obscure abaxially), sometimes glabrous adaxially. |
Cauline leaves | 0. |
usually 0 (or 1, as a bract); sessile; blade linear to oblong, margins entire, surfaces pubescent as basal. |
Racemes | 7–20-flowered, ebracteate, considerably elongated in fruit; rachis not flexuous (straight), glabrous. |
3–14(–30)-flowered, usually ebracteate, rarely proximalmost flowers bracteate, elongated in fruit; rachis not flexuous, glabrous or pubescent as stem. |
Flowers | sepals (erect), oblong or ovate, 2–2.7 mm (lateral pair subsaccate basally), glabrous or abaxially sparsely pilose, (trichomes simple); petals yellow, narrowly obovate, 4–6 × 2–3 mm, (apex emarginate); anthers ovate-subcordate, 0.4–0.5 mm. |
sepals broadly ovate, 2.5–3.5(–4) mm, pubescent, (trichomes simple and 2- or 3-rayed); petals yellow (fading white), oblanceolate to obovate, 4–6 × 1.5–2.5 mm; anthers ovate, 0.3–0.5 mm. |
Fruiting pedicels | divaricate, straight or curved, (often filiform), 5–18(–23) mm, glabrous. |
ascending, straight, (2.5–)4–11(–27) mm, glabrous or pubescent, trichomes 2–5-rayed or pectinate. |
Fruits | usually oblong to elliptic, rarely sublinear, plane, flattened, 4–8 × 1.5–2.2 mm; valves glabrous, (obscurely veined); ovules 24–30 per ovary; style 0.5–1 mm. |
broadly ovate to lanceolate, plane, flattened, 5–9(–11) × 2–4 mm; valves glabrous or puberulent, trichomes simple and 2-rayed, 0.05–0.3 mm; ovules 8–16(–20) per ovary; style 0.2–0.9 mm. |
Seeds | (brown), ovoid, 0.9–1.2 × 0.5–0.6 mm. |
oblong, 1.1–1.5 × 0.7–1 mm. |
2n | = 16. |
= 112. |
Draba sibirica |
Draba incerta |
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Phenology | Flowering May–Jul. | Flowering Jun–Aug. |
Habitat | Wet places on rocky slopes | Rock outcrops, talus, gravelly areas, tundra |
Elevation | 0-300 m (0-1000 ft) | 0-3300 m (0-10800 ft) |
Distribution |
Greenland; Europe (Russia); Asia (Caucasus, Iran, Russian Far East, Siberia, Turkey, central republics) |
AK; CO; ID; MT; NV; UT; WA; WY; AB; BC; QC; YT
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Discussion | Draba sibirica is one of three species of the genus in North America exhibiting malpighiaceous trichomes. It is easily distinguished from others (D. malpighiacea and some plants of D. spectabilis) by a complete absence of cauline leaves. It is found in the flora area in northeastern Greenland. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Draba incerta was shown by G. A. Mulligan (1972) to be sexually reproducing and 14-ploid with x = 8. It is often confused with the apomict D. oligosperma (2n = 32, 64). Draba incerta is readily separated from D. oligosperma by having well-formed (versus abortive) anthers and pollen, stalked (versus sessile) leaf trichomes, and ciliate (versus non-ciliate) basal leaves with obscure (versus prominent) midveins. Although both species have leafless scapes, one often finds a bract adnate to, or subtending, the proximalmost pedicel in D. incerta. Draba incerta is found near sea level in Alaska. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 337. | FNA vol. 7, p. 313. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Lepidium sibiricum, D. gmelinii, D. repens, D. sibirica subsp. arctica | D. exalata, D. incerta var. laevicapsula, D. incerta var. peasei, D. laevicapsula, D. peasei |
Name authority | (Pallas) Thellung: Neue Denkschr. Schweiz. Naturf. Ges. 41: 318. (1907) | Payson: Amer. J. Bot. 4: 261. (1917) |
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