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FNA | Family List | FNA Vol. 7 | Brassicaceae

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.

Group 10

1 Abaxial surface of leaf blades with pectinate, subdendritic, or some 7-12-rayed, stellate trichomes   (2)
+ Abaxial surface of leaf blades with 2-6-rayed trichomes   (14)
2 (1) Styles 1.5-3(-3.8) mm; seeds winged; anthers 0.7-0.9 mm.   88 Draba pterosperma
+ Styles (0.05-)0.1-1(-1.2) mm; seeds not winged; anthers 0.2-0.7 mm   (3)
3 (2) Abaxial surface of leaf blades with some pectinate trichomes   (4)
+ Abaxial surface of leaf blades with stellate or subdendritic trichomes   (5)
4 (3) Fruits 5-9(-11) mm, flattened; petals 4-6 mm; sepals 2.5-3.5(-4) mm; leaf blades usually with obscure midveins.   48 Draba incerta (in part)
+ Fruits 3-6(-7) mm, inflated; petals 2.5-4 mm; sepals 1.5-3 mm; leaf blades with prominent midveins.   73 Draba oligosperma (in part)
5 (3) Fruit valves pubescent, trichomes 2-6-rayed   (6)
+ Fruit valves glabrous or pubescent to puberulent, trichomes primarily simple and 2-rayed   (9)
6 (5) Plants not pulvinate; leaf blades 0.4-2.3(-3) cm × 1-6.5 mm; petals white; ovules 20-42 per ovary   (7)
+ Plants pulvinate; leaf blades 0.2-0.8 cm × 0.5-1.5(-2) mm; petals yellow; ovules 4-12(-16) per ovary   (8)
7 (6) Basal leaf blades apically with simple trichomes, midveins distinct abaxially; seeds 0.8-1.1 × (0.6-)0.7-0.8 mm.   7 Draba arctica (in part)
+ Basal leaf blades apically without simple trichomes, midveins obscure abaxially; seeds 0.6-0.8 × 0.4-0.6 mm.   25 Draba cinerea (in part)
8 (6) Fruits inflated basally (symmetric), plane, (2.5-)3-4(-5) mm; Alberta, British Columbia, California, Montana, Utah, Wyoming.   70 Draba novolympica (in part)
+ Fruits flattened (asymmetric), twisted or plane, 4-8(-10) mm; ec California.   100 Draba sierrae (in part)
9 (5) Seeds 1.5-2.2 × 1-1.4 mm; fruits 3-5 mm wide; styles 0.5-1.2 mm; petals yellow; ovules 8-16 per ovary   (10)
+ Seeds 0.7-1.3 × 0.5-0.8 mm; fruits 1-2.5(-3) mm wide (-5 mm wide in D. oxycarpa); styles 0.05-0.6(-1 in D. scotteri) mm; petals white or creamy white (yellow in D. scotteri and, sometimes, D. oxycarpa); ovules (10-) 12-28 per ovary   (11)
10 (9) Leaf blades each with prominent midvein; basal blades linear to linear-oblanceolate, 0.8-1.5 mm wide; petals pale yellow; fruits slightly inflated basally; w Montana, nw Wyoming.   79 Draba paysonii (in part)
+ Leaf blades each with obscure midvein; basal blades oblanceolate to obovate or suborbicular, 2-4.5 mm wide; petals bright yellow; fruits flattened; Alaska, British Columbia, Washington, Yukon.   93 Draba ruaxes (in part)
11 (9) Rachises often slightly flexuous; petals 2-3.5 × 1-1.5 mm; fruits linear to narrowly lanceolate or narrowly oblong, slightly twisted or plane.   57 Draba lonchocarpa (in part)
+ Rachises not flexuous; petals 3-5.5 × 1.5-3.5 mm; fruits ovate, oblong, lanceolate, or broadly so, rarely narrowly lanceolate, plane   (12)
12 (11) Fruits 3-5 mm wide; fruiting pedicels often curved upwards; leaf blade margins usually denticulate.   75 Draba oxycarpa (in part)
+ Fruits 1.5-3 mm wide; fruiting pedicels straight; leaf blade margins usually entire, rarely denticulate (D. lactea)   (13)
13 (12) Petals white; fruits 4-8 mm, valves glabrous.   55 Draba lactea (in part)
+ Petals yellow; fruits 5-11 mm, valves pubescent.   96 Draba scotteri
14 (1) Ovules (16-)18-36 per ovary   (15)
+ Ovules 4-14(-16) per ovary   (20)
15 (14) Styles (0.8-)1.2-3.5 mm; racemes 12-43-flowered; s California.   95 Draba saxosa (in part)
+ Styles 0.01-0.7 mm; racemes 2-12(-23)-flowered; Alaska, Canada, Greenland   (16)
16 (15) Fruits linear to linear-elliptic, (8-)10-17(-20) × 1.5-2 mm; plants not cespitose, caudex simple.   108 Draba stenoloba (in part)
+ Fruits oblong, ovate, or lanceolate, 4-12 × 2-5.5 mm; plants often cespitose, caudex branched   (17)
17 (16) Leaf blade margins entire   (18)
+ Leaf blade margins dentate or denticulate   (19)
18 (17) Petals 4-6 × 3-5 mm; fruits 3.5-5.5 mm wide (stigmas distinctly wider than styles); racemes not elongated (corymbose) in fruit.   27 Draba corymbosa (in part)
+ Petals 2-3 × (0.7-)1-1.5 mm; fruits 2-3.2 mm wide (stigmas narrower than styles); racemes mostly elongated in fruit.   62 Draba micropetala (in part)
19 (17) Fruits oblong to lanceolate-elliptic, 4-8 × 2-3 mm; fruiting pedicels straight, suberect to ascending, often subappressed to rachises; petals white, 2.5-4 mm.   69 Draba norvegica (in part)
+ Fruits ovate to ovate-oblong, 5-10 × 3-5 mm; fruiting pedicels curved upwards, subhorizontal to divaricate-ascending, not appressed to rachises; petals yellow or creamy white, 3.5-5 mm.   75 Draba oxycarpa (in part)
20 (14) Fruits inflated (at least basally), usually ovoid, subglobose, or ellipsoid, rarely lanceolate   (21)
+ Fruits flattened, ovate, lanceolate, oblong, or elliptic   (25)
21 (20) Leaf blades (1-)2-4(-6) mm wide; fruit valves glabrous or pubescent, trichomes simple and 2(-4)-rayed   (22)
+ Leaf blades 0.5-1.5 mm wide; fruit valves pubescent, trichomes 2-6-rayed   (23)
22 (21) Racemes 3-10(-13)-flowered; fruiting pedicels horizontal to divaricate, curved, glabrous (at least adaxially); ovules 10-16 per ovary; Alaska, Alberta, British Columbia, Montana, Yukon.   59 Draba macounii (in part)
+ Racemes (5-)9-18(-23)-flowered; fruiting pedicels divaricate-ascending, usually straight, rarely curved, pubescent; ovules (4-)8-12 per ovary; sc Utah.   103 Draba sobolifera (in part)
23 (21) Adaxial surface of leaf blades with simple and 4-6-rayed trichomes; fruit valves with 4-rayed trichomes (some rays spurred).   115 Draba trichocarpa (in part)
+ Adaxial surface of leaf blades with simple and 2-rayed trichomes; fruit valves with 2-6-rayed and simple trichomes   (24)
24 (23) Fruits (2.5-)3-4(-5) × 1.5-3.5 mm; petals bright yellow, 2-3.5(-4) mm; styles 0.2-0.6(-0.8) mm.   70 Draba novolympica (in part)
+ Fruits (5-)6-9 × (3-)3.7-5 mm; petals pale yellow, (4-)5-6 mm; styles (0.6-)0.8-1.2 mm.   79 Draba paysonii (in part)
25 (20) Abaxial surface of leaf blades with only 2-rayed trichomes.   56 Draba lemmonii (in part)
+ Abaxial surface of leaf blades glabrous or with 2-4-rayed and simple trichomes   (26)
26 (25) Adaxial surface of leaf blades pubescent with simple and 2-4-rayed trichomes   (27)
+ Adaxial surface of leaf blades glabrous (at least proximally), usually pubescent distally with simple trichomes   (29)
27 (26) Styles (0.8-)1.2-3.5 mm; petals linear-oblanceolate, 0.5-1 mm wide; racemes 12-43-flowered; s California.   95 Draba saxosa (in part)
+ Styles 0.2-0.9(-1.1) mm; petals obovate, 2-3.5 mm wide; racemes 2-10 (-14)-flowered; Alaska, Canada, Greenland, Washington   (28)
28 (27) Racemes (corymbose) not or slightly elongated in fruit; fruits 6-12 mm; seeds 1-1.3 × 0.6-0.9 mm.   27 Draba corymbosa (in part)
+ Racemes elongated in fruit; fruits 4-8(-10) mm; seeds 1.5-2 × 1-1.3 mm.   93 Draba ruaxes (in part)
29 (26) Styles 0.3-0.6(-1) mm; petals pale yellow, 2-5 mm; leaf blades each with prominent midvein.   35 Draba densifolia
+ Styles (0.8-)1-4.5 mm; petals white, 4.5-6.5 mm; leaf blades each with obscure midvein   (30)
30 (29) Styles (0.8-)1-1.7(-2) mm; leaf blades oblong-linear to narrowly oblanceolate, 1-2 mm wide; anthers ovate, 0.5-0.6 mm; c Idaho.   45 Draba hitchcockii
+ Styles (1.2-)2-4(-4.5) mm; leaf blades oblanceolate to obovate, 1.5-3.5 mm wide; anthers oblong, 0.8-1 mm; s Nevada.   51 Draba jaegeri

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