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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] [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 9

1 Abaxial surface of leaf blades usually with simple and/or 2-rayed trichomes, rarely glabrous   (2)
+ Abaxial surface of leaf blades with simple and 2-6-rayed trichomes, sometimes subdendritic and up to 12-rayed   (8)
       
2 (1) Sepals persistent   (3)
+ Sepals caducous   (4)
       
3 (2) Petals yellow, 3.5-5 × 1.5-2 mm; styles 0.4-1 mm; fruiting pedicels 3-7 mm; fruits 2.5-5 mm wide, flattened.   58 Draba longisquamosa
+ Petals white, 1.5-2 × 0.5-0.6 mm; styles 0.1-0.2 mm; fruiting pedicels 1-2.5(-4) mm; fruits (1.2-)1.5-2.5 mm wide, slightly inflated basally.   64 Draba monoensis (in part)
       
4 (2) Abaxial surface of leaf blades glabrous, midvein prominent; plants pulvinate.   35 Draba densifolia (in part)
+ Abaxial surface of leaf blades usually pubescent, sometimes glabrous (D. cyclomorpha), midvein usually obscure (except D. subcapitata); plants often not pulvinate   (5)
       
5 (4) Petals 1.4-4 × 0.5-1 mm; racemes 1-8 (or 9)-flowered, not or slightly elongated in fruit; Alaska, Canada, Greenland   (6)
+ Petals 4-6 × 1.5-2.5 mm; racemes 4-15(-21)-flowered, elongated in fruit; California, Oregon   (7)
       
6 (5) Petals yellow or yellowish green, linear-oblanceolate, 3-4 × 0.5-0.8 mm; leaf blades each with midvein usually obscured; ovules 4-8 per ovary; Alaska.   3 Draba aleutica
+ Petals white or creamy white, spatulate, 1.5-2(-2.5) × 0.7-1 mm; leaf blades each with midvein strongly thickened; ovules 14-24 per ovary; Alaska, Greenland, Northwest Territories, Nunavut, Quebec.   113 Draba subcapitata (in part)
       
7 (5) Fruits plane, valves glabrous; fruiting pedicels softly pilose; ovules 8-12 per ovary; seeds 1.4-1.9 × 1-1.2 mm; ne Oregon.   33 Draba cyclomorpha
+ Fruits slightly twisted, valves pubescent; fruiting pedicels hirsute; ovules 10-16 per ovary; seeds 1-1.4 × 0.6-1 mm; ec California.   56 Draba lemmonii
       
8 (1) Racemes not or slightly elongated (sometimes subumbellate) in fruit   (9)
+ Racemes elongated in fruit   (13)
       
9 (8) Abaxial surface of leaf blades with 2-5-rayed trichomes; fruit valves glabrous; petals 1-2 mm wide.   59 Draba macounii (in part)
+ Abaxial surface of leaf blades with some simple trichomes; fruit valves pubescent or puberulent (sometimes glabrous in D. stenopetala and D. subcapitata); petals 0.3-1.5 mm wide   (10)
       
10 (9) Basal leaves densely imbricate; fruits 3-6 mm, inflated (at least basally)   (11)
+ Basal leaves not imbricate; fruits 5-10 mm, flattened   (12)
       
11 (10) Petals usually yellow, rarely purple, linear, 2.5-5 × 0.3-0.7 mm; ovules 4-10 per ovary.   109 Draba stenopetala (in part)
+ Petals white or creamy white, spatulate, 1.5-2(-2.5) × 0.7-1 mm; ovules 14-24 per ovary.   113 Draba subcapitata (in part)
       
12 (10) Fruits ovate-elliptic, 2-3.2 mm wide, valves often densely pubescent; ovules (16-)18-28 per ovary; leaf blades with apices obtuse to rounded, surfaces with subcruciform trichomes.   62 Draba micropetala (in part)
+ Fruits obovate, (3-)3.5-5 mm wide, valves often glabrate; ovules 8-16 (-20) per ovary; leaf blades with apices acute or subacute, surfaces with simple and/or 2-branched trichomes.   77 Draba pauciflora
       
13 (8) Plants stoloniferous; basal leaves not rosulate; fruit valves glabrous.   72 Draba ogilviensis (in part)
+ Plants cespitose, not stoloniferous; basal leaves rosulate; fruit valves pubescent or glabrous   (14)
       
14 (13) Petals linear, 0.3-0.7 mm wide; fruits inflated basally; ovules 4-10 per ovary.   109 Draba stenopetala (in part)
+ Petals obovate, spatulate, or narrowly oblanceolate, (0.7-)1-4.6 mm wide; fruits flattened; ovules 12-36 per ovary   (15)
       
15 (14) Petals white; fruit valves pubescent, trichomes 2-5-rayed; stigmas distinctly wider than styles; abaxial surface of leaf blades with some 6-12-rayed trichomes   (16)
+ Petals pale or bright yellow (sometimes creamy white in D. oxycarpa); fruit valves usually pubescent, sometimes glabrous, trichomes simple, spurred, or 2-rayed; stigmas about as wide as styles; abaxial surface of leaf blades with 2-5-rayed trichomes (rays sometimes spurred in D. oxycarpa)   (17)
       
16 (15) Fruits with 2-4-rayed and, sometimes, simple trichomes; petals 3-4 mm; stems proximally with branched trichomes 2-6-rayed.   8 Draba arctogena (in part)
+ Fruits with (2-)5-12-rayed trichomes; petals 3.5-5 mm; stems proximally with branched trichomes 4-10-rayed.   71 Draba oblongata (in part)
       
17 (15) Fruiting pedicels 1-3(-4) mm; petals 2-3 × (0.7-)1-1.5 mm; styles 0.05- 0.3 mm; racemes slightly elongated in fruit.   62 Draba micropetala (in part)
+ Fruiting pedicels (2.5-)4-13(-30) mm; petals 3.5-6 × 1.7-4.6 mm; styles (0.1-)0.2-0.9 mm; racemes often considerably elongated in fruit   (18)
       
18 (17) Basal leaf blades linear to linear-oblanceolate, 1-2.5(-4) mm wide, midveins prominent.   84 Draba pilosa (in part)
+ Basal leaf blades oblong, lanceolate, oblanceolate, or obovate, 2-9 mm wide, midveins obscure   (19)
       
19 (18) Petals 1.7-2.5 mm wide; sepals purplish tinged; fruits elliptic; abaxial surface of leaf blades with 2-4-rayed trichomes; seeds pale brown.   4 Draba alpina
+ Petals 2.5-4.6 mm wide; sepals gray-green; fruits ovate, ovate-oblong, or lanceolate; abaxial surface of leaf blades with 2-5-rayed and subdendritic trichomes; seeds dark brown or black   (20)
       
20 (19) Basal leaf blade margins usually denticulate; fruits ovate to ovate-oblong, 3-5 mm wide; styles 0.2-0.6 mm; Greenland.   75 Draba oxycarpa (in part)
+ Basal leaf blade margins entire; fruits lanceolate, 2.3-3.8 mm wide; styles 0.1-0.3 mm; Canada.   101 Draba simmonsii

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