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9. Draba Linnaeus, Sp. Pl. 2: 642. 1753; Gen. Pl. ed. 5, 291. 1754.
[Greek drabe, acrid, for taste of mustard plant]
Ihsan A. Al-Shehbaz, Michael D. Windham, Reidar Elven
Abdra Greene; Erophila de Candolle; Nesodraba Greene; Tomostima Rafinesque
Annuals, biennials, or perennials [subshrubs]; (caudex simple or branched); scapose or not; glabrous or pubescent, trichomes stalked or sessile, simple, forked, cruciform, stellate, malpighiaceous, or dendritic, often more than 1 kind present. Stems usually erect to ascending, sometimes decumbent or prostrate, unbranched or branched (usually distally). Leaves usually basal and cauline, sometimes cauline absent; petiolate or sessile; basal usually rosulate, usually petiolate, rarely sessile, blade margins usually entire or toothed, rarely pinnately lobed; cauline (when present), petiolate or sessile, blade (base cuneate [auriculate]), margins entire or dentate. Racemes (often corymbose, sometimes bracteate), elongated or not in fruit. Fruiting pedicels (proximalmost) erect or ascending to divaricate, slender. Flowers: sepals (rarely persistent), erect, ascending, or, rarely, spreading, ovate or oblong [elliptic], lateral pair not saccate or subsaccate basally; petals (erect or ascending to patent), yellow, white, pink, purple, or orange [red], obovate, spatulate, oblanceolate, or linear [orbicular, oblong], (longer than or, rarely, shorter than sepals), claw obscurely to well-differentiated from blade, (apex obtuse, rounded, notched, or, rarely, deeply 2-lobed); stamens slightly to strongly tetradynamous; filaments dilated or not basally, (glabrous); anthers ovate or oblong, (not apiculate); nectar glands (1, 2, or 4), distinct or confluent, subtending bases of stamens, median glands present or absent. Fruits silicles or siliques, sessile, ovate, lanceolate, elliptic, oblong, linear, suborbicular, ovoid, or subglobose, plane or spirally twisted, smooth, (not keeled, unappendaged), usually latiseptate, rarely terete; valves (papery), each with distinct or obscure midvein and lateral veins, glabrous or pubescent; replum rounded; septum complete; ovules 4-70(-88) per ovary; style obsolete or distinct; stigma capitate. Seeds biseriate, oblong, ovate, or orbicular, usually flattened (slightly flattened in D. aleutica, D. verna), usually not winged (winged in D. asterophora, D. brachycarpa, D. carnosula, D. pterosperma); seed coat (minutely reticulate), not mucilaginous when wetted; cotyledons accumbent. x = 6-12.
Species ca. 380 (121 in the flora): North America, Mexico, South America (Andes, Colombia to Patagonia), Europe, Asia, nw Africa; alpine and boreal, rarely in temperate and low-elevation areas of North America and Eurasia.
SELECTED REFERENCES Beilstein, M. A. and M. D. Windham. 2003. A phylogenetic analysis of western North American Draba (Brassicaceae) based on nuclear ribosomal DNA sequences from the ITS region. Syst. Bot. 28: 584-592. Ekman, E. 1929. Studies in the genus Draba. Svensk Bot. Tidskr. 23: 476-495. Ekman, E. 1930. Contribution to the Draba flora of Greenland. II. Svensk Bot. Tidskr. 24: 280-297. Ekman, E. 1931. Contribution to the Draba flora of Greenland. III. Some notes on the arctic, especially the Greenland drabas of the sections Aizopsis and Chrysodraba DC. Svensk Bot. Tidskr. 25: 465-494. Ekman, E. 1932. Contribution to the Draba flora of Greenland. IV. Svensk Bot. Tidskr. 26: 431-447. Fernald, M. L. 1934. Draba in temperate northeastern America. Rhodora 36: 241-261, 285-305, 314-344, 353-371, 392-404. Hitchcock, C. L. 1941. A Revision of the Drabas of Western North America. Seattle. [Univ. Wash. Publ. Biol. 11.] Koch, M. and I. A. Al-Shehbaz. 2002. Molecular data indicate complex intra- and intercontinental differentiation of American Draba (Brassicaceae). Ann. Missouri Bot. Gard. 89: 88-109. Mulligan, G. A. 1976. The genus Draba in Canada and Alaska: Key and summary. Canad. J. Bot. 54: 1386-1393. Payson, E. B. 1917. The perennial scapose drabas of North America. Amer. J. Bot. 4: 253-267. Schulz, O. E. 1927. Cruciferae—Draba, Erophila. In: H. G. A. Engler, ed. 1900-1953. Das Pflanzenreich…. 107 vols. Berlin. Vol. 89[IV,105], pp. 1-396.
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Group 5
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| 1 |
Fruit trichomes 2-rayed and/or simple |
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(2) |
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Fruit trichomes 4-rayed (some) (except D. saxosa 2- or 3-rayed) |
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(12) |
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| 2 (1) |
Stem and leaf trichomes sessile, 2 rays parallel to long axis of stem or midvein, some trichomes malpighiaceous. |
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104 Draba spectabilis (in part) |
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Stem and leaf trichomes stalked, rays not parallel to long axis of stem or midvein, not malpighiaceous |
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(3) |
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| 3 (2) |
Abaxial surface of basal leaf blades with cruciform trichomes |
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(4) |
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Abaxial surface of basal leaf blades with 2-6-rayed trichomes |
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(5) |
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| 4 (3) |
Fruits plane; styles 0.2-0.7 mm; Alaska, Canada. |
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52 Draba juvenilis (in part) |
| + |
Fruits often strongly twisted; styles 0.8-1.8(-2.5) mm; Arizona. |
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83 Draba petrophila |
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| 5 (3) |
Fruits appressed or subappressed to rachises; proximalmost flowers bracteate. |
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13 Draba aurea (in part) |
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Fruits not appressed to rachises; proximalmost flowers ebracteate |
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(6) |
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| 6 (5) |
Styles (1-)1.5-3.5 mm. |
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44 Draba helleriana (in part) |
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Styles usually 0.01-0.9 mm, if longer (D. pennellii), plants pulvinate or petals white |
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(7) |
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| 7 (6) |
Plants not cespitose or pulvinate, caudex simple or poorly developed; fruits (7-)10-17(-20) mm; ovules 20-36(-42) per ovary |
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(8) |
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Plants cespitose or pulvinate, caudex branched; fruits (3-)4-9 (-14) mm; ovules (4-)8-24 per ovary |
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(9) |
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| 8 (7) |
Fruits narrowly elliptic to lanceolate, 2-3.5 mm wide; styles 0.2-0.6(-0.8) mm; racemes (5-)10-35(-47)-flowered; ne Nevada, Utah. |
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18 Draba brachystylis (in part) |
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Fruits linear to linear-elliptic, 1.5-2 mm wide; styles 0.01-0.15 mm; racemes (2-)4-10(-15)-flowered; Alaska, Alberta, British Columbia, Washington, Yukon. |
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108 Draba stenoloba (in part) |
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| 9 (7) |
Seeds 1.8-2.8 × 1.2-2 mm, winged. |
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12 Draba asterophora (in part) |
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Seeds 0.7-1.8 × 0.4-1 mm, not winged |
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(10) |
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| 10 (9) |
Petals white; cauline leaves 1-4; styles (0.7-)1-1.8(-2.1) mm; fruits slightly twisted or plane; e Nevada. |
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82 Draba pennellii (in part) |
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Petals yellow (or fading white); cauline leaves 1; styles 0.2-0.9 mm; fruits plane; Nevada and elsewhere |
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(11) |
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| 11 (10) |
Fruits flattened; abaxial surface of leaf blades with pectinate and sometime 4-6-rayed trichomes; petals yellow (fading white), 4-6 mm. |
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48 Draba incerta (in part) |
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Fruits inflated (at least basally); abaxial surface of leaf blades with 2-4-rayed trichomes; petals yellow, 3-4 mm. |
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103 Draba sobolifera (in part) |
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| 12 (1) |
Caudices simple, plants not cespitose |
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(13) |
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Caudices branched, plants cespitose (branches sometimes surculose or rhizomatous) |
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(18) |
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| 13 (12) |
Petals white; styles 0.03-0.1(-0.15) mm. |
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87 Draba praealta (in part) |
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Petals yellow, rarely fading whitish; styles (0.5-)0.9-3.5 mm |
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(14) |
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| 14 (13) |
Cauline leaves 1-5; sepals with 2-4-rayed trichomes |
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(15) |
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Cauline leaves 5-33(-43); sepals glabrous or with some simple trichomes |
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(16) |
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| 15 (14) |
Petals (5-)6-8.5 × 2.2-3.5 mm; fruits slightly twisted; ovules 24-36 per ovary; styles (0.8-)1-2.2 mm; se Arizona, w New Mexico. |
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63 Draba mogollonica (in part) |
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Petals 3-5 × 1-1.5 mm; fruits plane; ovules 14-22 per ovary; styles 0.9-1.2 mm; nc Utah. |
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94 Draba santaquinensis (in part) |
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| 16 (14) |
Fruits 3-5 mm wide, plane; stems 0.3-1.5 dm; petals 0.5-1(-1.2) mm wide. |
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14 Draba aureola |
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Fruits 2-3.5 mm wide, usually twisted, rarely plane; stems (0.5-)1-4.3 (-5.2) dm; petals 1.5-2.5 mm wide |
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(17) |
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| 17 (16) |
Styles 0.5-1.2(-1.5) mm; petals 3.5-5 mm; ovules 28-38(-44) per ovary; fruits often subappressed to rachises. |
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13 Draba aurea (in part) |
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Styles (1-)1.5-3.5 mm; petals 5-7 mm; ovules 14-28 per ovary; fruits not appressed to rachises. |
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44 Draba helleriana (in part) |
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| 18 (12) |
Basal and often cauline leaf blade margins dentate; petals white |
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(19) |
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Basal and cauline leaf blade margins usually entire, sometimes denticulate (D. viridis); petals yellow (unknown in D. trichocarpa) |
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(21) |
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| 19 (18) |
Styles (1-)1.5-3(-4) mm (sparsely pubescent); ovules 4-10(-12) per ovary; fruits often strongly twisted. |
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89 Draba ramosissima |
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Styles (0.01-)0.1-0.6(-0.8) mm (glabrous); ovules 16-28(-30) per ovary; fruits plane or slightly twisted |
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(20) |
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| 20 (19) |
Petals 4-6 mm; fruits (5-)7-12 × 2.5-4.5 mm, slightly twisted or plane; Alaska, w Canada. |
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16 Draba borealis (in part) |
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Petals 2.5-4 mm; fruits 4-8 × 2-3 mm, plane; e Canada, Greenland. |
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69 Draba norvegica |
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| 21 (18) |
Styles 0.3-1.2(-1.4) mm; ovules 8-12 per ovary; Idaho, Nevada |
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(22) |
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Styles (0.7-)1.2-3.5 mm; ovules 8-24 per ovary; s Arizona, California, s Oregon |
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(23) |
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| 22 (21) |
Basal leaf blades 6-19(-24) × 2-5(-8) mm; styles 0.5-1.2(-1.4) mm; petals 3.5-5 mm; fruiting pedicels (3-)4-8 mm; Nevada. |
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10 Draba arida |
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Basal leaf blades 2-4 × 0.5-1.5 mm; styles 0.3-0.7 mm; petals 2-4 mm; fruiting pedicels 1-4.5 mm; Idaho. |
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115 Draba trichocarpa (in part) |
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| 23 (21) |
Cauline leaves 5-16; fruits 3.5-8 mm; leaf blade surfaces with cruciform trichomes; s Arizona. |
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118 Draba viridis |
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Cauline leaves 1-3 (or 4); fruits 6-11(-15) mm; leaf blade surfaces with 2- or 3-rayed trichomes; California, Oregon |
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(24) |
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| 24 (23) |
Petals 5.5-8 mm; cauline leaves 1-3 (or 4); fruits lanceolate to broadly ovate, plane; n California, s Oregon. |
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46 Draba howellii (in part) |
| + |
Petals 3-3.5 mm; cauline leaves 1; fruits oblong to linear-oblong, slightly twisted or plane; s California. |
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95 Draba saxosa (in part) |
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List of Keys
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List of lower taxa
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