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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 6

1 Branched trichomes sessile, malpighiaceous; Greenland.   99 Draba sibirica (in part)
+ Branched trichomes stalked, not malpighiaceous, sometimes only simple cilia present; not Greenland (except D. crassifolia and D. lactea)   (2)
       
2 (1) Fruits 10-23 mm; seeds orbicular, 3-4.5 mm, broadly winged.   23 Draba carnosula
+ Fruits 2.5-11(-16) mm; seeds ovoid, oblong, or elliptic, 0.7-2(-2.6) mm, not winged   (3)
       
3 (2) Plants stoloniferous; basal leaves not rosulate.   72 Draba ogilviensis (in part)
+ Plants not stoloniferous (usually cespitose or pulvinate); basal leaves rosulate   (4)
       
4 (3) Petals white   (5)
+ Petals yellow (rarely fading white)   (10)
       
5 (4) Petals 5-6.5 mm; styles 0.6-1.8(-2.5) mm; Nevada.   97 Draba serpentina
+ Petals 2.5-4.5(-5) mm; styles 0.1-0.9(-1.2) mm; not Nevada   (6)
       
6 (5) Fruits inflated (at least basally); racemes (6-)10-28(-40)-flowered.   112 Draba subalpina (in part)
+ Fruits flattened; racemes 2-8(-12)-flowered   (7)
       
7 (6) Ovules (10-)14-22(-26) per ovary; petals 1.8-3 mm wide; Alaska, Canada, Greenland   (8)
+ Ovules 8-16 per ovary; petals 1.2-2 mm wide; Idaho, Montana, Utah, Wyoming   (9)
       
8 (7) Petiole and midvein of basal leaves thickened; basal leaves (1-)2-6 mm wide; styles 0.1-0.4 mm.   55 Draba lactea (in part)
+ Petiole and midvein of basal leaves not thickened; basal leaves 1-2 mm wide; styles 0.4-1 mm.   65 Draba mulliganii (in part)
       
9 (7) Basal leaf blade apex acute; fruits ovate, plane, 2.5-4 mm wide; fruiting pedicels 2-6 mm; sepals persistent.   39 Draba globosa (in part)
+ Basal leaf blade apex obtuse; fruits ± oblong, slightly twisted, 1.5-3 mm wide; fruiting pedicels 4-13 mm; sepals caducous.   74 Draba oreibata
       
10 (4) Fruits inflated (at least basally)   (11)
+ Fruits flattened   (12)
       
11 (10) Adaxial surface of leaf blades with simple and 2-rayed trichomes; styles 0.1-0.5 mm.   59 Draba macounii (in part)
+ Adaxial surface of leaf blades with 2-4-rayed trichomes; styles 0.3-1(-1.3) mm.   106 Draba sphaeroides (in part)
       
12 (10) Styles (0.5-)0.7-3 mm; petals (4-)5-8 mm; sepals 2-4 mm   (13)
+ Styles 0.02-0.8(-1) mm; petals 1.5-4(-6) mm; sepals 1-3 mm   (15)
       
13 (12) Leaf blade margins ciliate with subsetiform, simple trichomes.   20 Draba burkei
+ Leaf blade margins not ciliate, often with some branched trichomes   (14)
       
14 (13) Fruits 6-11(-15) × 3-5 mm; styles (0.7-)1.6-3 mm; ovules 8-22 per ovary; California, Oregon.   46 Draba howellii (in part)
+ Fruits (3-)4-6.5(-8) × 2-3.2 mm; styles 0.6-1.7 mm; ovules 4-8 per ovary; Utah.   60 Draba maguirei (in part)
       
15 (12) Plants without sterile rosettes or shoots, not pulvinate or matted, caudex simple or branched; petals 0.5-1 mm wide; ovules (8-)16-24(-30) per ovary; seeds 0.7-0.8 mm.   29 Draba crassifolia (in part)
+ Plants often with sterile rosettes or shoots, pulvinate or loosely matted, caudex branched; petals 1-3 mm wide; ovules 4-16 per ovary; seeds 1-2(-2.6) mm   (16)
       
16 (15) Fruiting pedicels decurrent basally.   49 Draba incrassata
+ Fruiting pedicels not decurrent basally   (17)
       
17 (16) Plants loosely matted; racemes considerably elongated in fruit.   30 Draba cruciata (in part)
+ Plants pulvinate; racemes not or slightly elongated in fruit   (18)
       
18 (17) Leaf blades with prominent midvein abaxially; fruit valves pubescent or puberulent.   35 Draba densifolia (in part)
+ Leaf blades with obscure midvein; fruit valves glabrous   (19)
       
19 (18) Leaves fleshy, blade apex obtuse; fruiting pedicels 4-10 mm; fruit valves obscurely veined.   34 Draba daviesiae
+ Leaves not fleshy, blade apex acute; fruiting pedicels 2-6 mm; fruit valves distinctly veined.   39 Draba globosa (in part)

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