Draba incerta |
Draba streptobrachia |
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whitlow-wort, Yellowstone Draba, Yellowstone Draba whitlow-wort, Yellowstone whitlow-grass, Yellowstone whitlow-wort |
alpine tundra 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; caudex branched (often with persistent leaf remains, branches not creeping); not 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–)0.2–1(–1.3) dm, pubescent throughout, trichomes subsessile (often crisped), 3–5-rayed, stellate, 0.03–0.25(–0.4) mm, (rays sometimes forked). |
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. |
rosulate; petiole (obscure), usually not ciliate, rarely sparsely pubescent, (trichomes simple, to 0.6 mm); blade oblanceolate to linear-oblanceolate, (0.4–)0.5–3(–4) cm × 1–5 mm, margins entire, surfaces pubescent with short-stalked (crisped), 3–8-rayed trichomes, 0.05–0.4 mm. |
Cauline leaves | usually 0 (or 1, as a bract); sessile; blade linear to oblong, margins entire, surfaces pubescent as basal. |
(1 or) 2–4 (or 5); sessile; blade oblong to ovate or linear, margins entire, surfaces pubescent as basal. |
Racemes | 3–14(–30)-flowered, usually ebracteate, rarely proximalmost flowers bracteate, elongated in fruit; rachis not flexuous, glabrous or pubescent as stem. |
4–10(–18)-flowered, ebracteate, elongated in fruit; rachis not flexuous, pubescent 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 ovate, 2–3 mm, pubescent, (trichomes simple and short-stalked, 2–4-rayed); petals yellow, spatulate, 3–5 × 1.5–3 mm, (clawed); anthers ovate, 0.25–0.4 mm. |
Fruiting pedicels | ascending, straight, (2.5–)4–11(–27) mm, glabrous or pubescent, trichomes 2–5-rayed or pectinate. |
ascending, usually straight, rarely curved upward, (2–)3–8(–12) mm, pubescent 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. |
(not appressed to rachis), ovate to elliptic or lanceolate, slightly twisted or plane, flattened, (3–)5–10 × 2–4 mm; valves often pubescent, occasionally glabrous, trichomes simple and minutely stalked, 2–4-rayed, 0.03–0.25 mm; ovules 10–16(–18) per ovary; style 0.3–0.8(–1.2) mm. |
Seeds | oblong, 1.1–1.5 × 0.7–1 mm. |
oblong, 1–1.6 × 0.6–1 mm. |
2n | = 112. |
= ca. 64. |
Draba incerta |
Draba streptobrachia |
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Phenology | Flowering Jun–Aug. | Flowering Jul–Aug. |
Habitat | Rock outcrops, talus, gravelly areas, tundra | Alpine tundra, scree, ridges and alpine slopes, turf, fellfields, talus slopes, crevices in rock ledges, loose soils |
Elevation | 0-3300 m (0-10800 ft) | 3200-4000 m (10500-13100 ft) |
Distribution |
AK; CO; ID; MT; NV; UT; WA; WY; AB; BC; QC; YT
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CO
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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.) |
As indicated by Price, Draba streptobrachia is an apomict, yielding abundant, well-developed seed despite producing only abortive pollen. Morphological studies (M. D. Windham, unpubl.) suggest that the species may be an allopolyploid containing a genome from D. crassa. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 313. | FNA vol. 7, p. 341. |
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 | D. chrysantha, D. spectabilis var. dasycarpa |
Name authority | Payson: Amer. J. Bot. 4: 261. (1917) | R. A. Price: Brittonia 32: 168. (1980) |
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