Draba incerta |
Draba hitchcockii |
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whitlow-wort, Yellowstone Draba, Yellowstone Draba whitlow-wort, Yellowstone whitlow-grass, Yellowstone whitlow-wort |
lost river Draba |
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Habit | Perennials; (cespitose, often pulvinate); caudex branched (dense with persistent leaf remains, branches sometimes terminating in sterile rosettes); scapose. | Perennials; (densely cespitose); caudex branched (densely covered with persistent leaves, branches sometimes terminating in sterile rosettes); scapose. |
Stems | 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). |
unbranched, (0.1–)0.3–1(–1.3) dm, hirsute throughout, trichomes simple, 0.4–1 mm, and 2–4-rayed, 0.1–0.6 mm. |
Basal leaves | 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. |
(densely imbricate); rosulate; sessile; blade narrowly oblanceolate to oblong-linear, 0.3–1.2(–1.5) cm × 1–2 mm, margins entire, (ciliate, trichomes simple, 0.3–1.2 mm), surfaces pubescent abaxially with stalked, 2–4-rayed trichomes, 0.08–0.45 mm, (midvein obscure), adaxially glabrous proximally, sparsely pubescent distally with mostly simple trichomes. |
Cauline leaves | usually 0 (or 1, as a bract); sessile; blade linear to oblong, margins entire, surfaces pubescent as basal. |
0. |
Racemes | 3–14(–30)-flowered, usually ebracteate, rarely proximalmost flowers bracteate, elongated in fruit; rachis not flexuous, glabrous or pubescent as stem. |
4–15-flowered, ebracteate, elongated in fruit; rachis not flexuous, hirsute as stem. |
Flowers | 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. |
sepals oblong, 2.5–3.5 mm, hirsute, (trichomes simple and stalked, 2–4-rayed); petals white, obovate, 5–6.5 × 2–3.5 mm; anthers ovate, 0.5–0.6 mm. |
Fruiting pedicels | ascending, straight, (2.5–)4–11(–27) mm, glabrous or pubescent, trichomes 2–5-rayed or pectinate. |
ascending, straight, (2–)4–13(–18) mm, hirsute as stem. |
Fruits | 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. |
ovate to broadly oblong or elliptic, plane, flattened, (3–)4–7(–10) × (2.5–)3.5–5 mm; valves pubescent, trichomes simple and short-stalked, 2(–4)-rayed, 0.06–0.5 mm; ovules 8–12 per ovary; style (0.8–)1–1.7(–2) mm. |
Seeds | oblong, 1.1–1.5 × 0.7–1 mm. |
oblong, 1.4–1.8 × 0.8–1 mm. |
2n | = 112. |
= 54. |
Draba incerta |
Draba hitchcockii |
|
Phenology | Flowering Jun–Aug. | Flowering May–Jun. |
Habitat | Rock outcrops, talus, gravelly areas, tundra | Limestone outcrops and gravelly soil |
Elevation | 0-3300 m (0-10800 ft) | 1800-2200 m (5900-7200 ft) |
Distribution |
AK; CO; ID; MT; NV; UT; WA; WY; AB; BC; QC; YT
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ID |
Discussion | 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.) |
Draba hitchcockii is known from the Lost River Range in Butte and Custer counties. Based on morphological and chromosomal evidence, M. D. Windham (2004) suggested that it may be an allopolyploid resulting from hybridization between D. oreibata and D. paysonii. Draba hitchcockii is superficially similar to D. jaegeri, a taxon known from the Charleston Mountains of Clark County, Nevada. Both are cespitose perennials with relatively large, white flowers and a chromosome number (2n = 54) otherwise unknown in Draba (Windham). Features distinguishing these two taxa are provided in the discussion of 51. D. jaegeri. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 313. | FNA vol. 7, p. 311. |
Parent taxa | Brassicaceae > tribe Arabideae > Draba | Brassicaceae > tribe Arabideae > Draba |
Sibling taxa | ||
Synonyms | D. exalata, D. incerta var. laevicapsula, D. incerta var. peasei, D. laevicapsula, D. peasei | |
Name authority | Payson: Amer. J. Bot. 4: 261. (1917) | Rollins: J. Arnold Arbor. 64: 500. (1983) |
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