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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 1

1 Cauline leaves 0   (2)
+ Cauline leaves 1-54(-76)   (7)
       
2 (1) Petals deeply 2-fid; rachises of fruiting racemes flexuous.   117 Draba verna
+ Petals usually obtuse, rarely emarginate; rachises of fruiting racemes usually straight, if flexuous then petals yellow   (3)
       
3 (2) Petals white; late-season flowers apetalous; fruit valves usually with antrorse, simple trichomes, rarely glabrous   (4)
+ Petals yellow; late-season flowers with petals; fruit valves usually glabrous, rarely puberulent   (5)
       
4 (3) Racemes 10-50(-70)-flowered, elongated in fruit, rachises densely pubescent; fruiting pedicels densely pubescent.   31 Draba cuneifolia (in part)
+ Racemes (3-)5-12(-16)-flowered, subumbellate in fruit, rachises usually glabrous, rarely sparsely pubescent; fruiting pedicels glabrous or sparsely pubescent.   92 Draba reptans (in part)
       
5 (3) Abaxial surface of leaf blades glabrous or sparsely pubescent, trichomes simple and 2-rayed; stems usually glabrous, rarely pubescent proximally, trichomes simple.   29 Draba crassifolia (in part)
+ Abaxial surface of leaf blades pubescent, trichomes 2-4-rayed; stems pubescent, trichomes 2-4-rayed (sometimes simple)   (6)
       
6 (5) Stems proximally with simple and 2-rayed trichomes; adaxial surface of leaf blades with simple and 2-rayed trichomes; anthers 0.15-0.25 mm; fruits (4-)6-12(-15) mm.   2 Draba albertina (in part)
+ Stems proximally with 2-4-rayed trichomes; adaxial surface of leaf blades with 2-4-rayed trichomes; anthers 0.25-0.4 mm; fruits (8-)10-17(-20) mm.   108 Draba stenoloba (in part)
       
7 (1) Styles (0.8-)1-3.5 mm   (8)
+ Styles 0.01-0.6 (-0.8) mm   (12)
       
8 (7) Adaxial surface of basal leaf blade pubescent with simple, subsetiform trichomes, rarely mixed with 2-rayed ones; fruit valves sparsely puberulent, trichomes simple.   15 Draba bifurcata (in part)
+ Adaxial surface of basal leaf blade pubescent with at least some 2-4-rayed trichomes; fruit valves usually pubescent, rarely glabrous, trichomes 2-4-rayed   (9)
       
9 (8) Petals linear, 0.2-0.5 mm wide; s California.   26 Draba corrugata (in part)
+ Petals oblanceolate to spatulate, 1-3.5 mm wide; se Arizona, Colorado, New Mexico, Utah   (10)
       
10 (9) Fruits plane, valves pubescent, trichomes 2-4-rayed; petals 3-5 × 1-1.5 mm, often fading whitish; Utah.   94 Draba santaquinensis (in part)
+ Fruits slightly to strongly twisted, valves glabrous, pubescent, or puberulent, trichomes simple and 2(-4)-rayed; petals 5-8.5 × 1.5-3.5 mm, not fading whitish; Arizona, Colorado, New Mexico   (11)
       
11 (10) Cauline leaves (8-)12-31(-43); rachises pubescent; fruiting pedicels 4-10(-13) mm.   44 Draba helleriana (in part)
+ Cauline leaves 1-3; rachises often glabrous or, rarely, sparsely pubescent; fruiting pedicels (6-)9-18(-22) mm.   63 Draba mogollonica (in part)
       
12 (7) Racemes bracteate basally; fruiting pedicels erect to ascending (subappressed to rachises); cauline leaves (15-)22-54(-76), densely overlapping proximally.   47 Draba incana
+ Racemes ebracteate; fruiting pedicels horizontal to divaricate-ascending (not appressed to rachises); cauline leaves 1-15(-25), seldom overlapping   (13)
       
13 (12) Rachises glabrous   (14)
+ Rachises pubescent   (18)
       
14 (13) Petals white or, rarely, absent; basal leaves not rosulate; racemes subumbellate in fruit.   92 Draba reptans (in part)
+ Petals yellow; basal leaves rosulate; racemes elongated in fruit   (15)
       
15 (14) Cauline leaves 4-12(-15); fruiting pedicels 7-28(-35) mm, (1.5-)2-7 times longer than fruit.   67 Draba nemorosa
+ Cauline leaves 1-3(-5); fruiting pedicels (1-)3-14(-19) mm, subequaling or shorter than fruit   (16)
       
16 (15) Abaxial surface of leaf blades glabrous or sparsely pubescent, trichomes simple and 2-rayed; stems usually glabrous, or, rarely, sparsely pubescent proximally, trichomes simple.   29 Draba crassifolia (in part)
+ Abaxial surface of leaf blades pubescent, trichomes 2-4-rayed; stems pubescent basally, trichomes 2-4-rayed (sometimes simple)   (17)
       
17 (16) Stems proximally with simple and 2-rayed trichomes; adaxial surface of leaf blades with simple and 2-rayed trichomes; anthers 0.15-0.25 mm; fruits (4-)6-12(-15) mm.   2 Draba albertina (in part)
+ Stems proximally with 2-4-rayed trichomes; adaxial surface of leaf blades with 2-4-rayed trichomes; anthers 0.25-0.4 mm; fruits (8-)10-17(-20) mm.   108 Draba stenoloba (in part)
       
18 (13) Leaf blade surfaces with cruciform trichomes   (19)
+ Leaf blade surfaces with simple and 2-7-rayed trichomes   (20)
       
19 (18) Fruit valves pubescent; ovules 4-6(-8) per ovary.   5 Draba aprica
+ Fruit valves glabrous; ovules 8-16(-20) per ovary.   17 Draba brachycarpa
       
20 (18) Fruits obovate to obovate-oblong.   85 Draba platycarpa
+ Fruits elliptic, oblong, linear, lanceolate, or, rarely, ovate   (21)
       
21 (20) Late-season flowers apetalous; basal leaves not rosulate   (22)
+ Late-season flowers with petals; basal leaves rosulate   (23)
       
22 (21) Racemes 10-50(-70)-flowered, elongated in fruit, rachises denselypubescent; fruiting pedicels densely pubescent.   31 Draba cuneifolia (in part)
+ Racemes (3-)5-12(-16)-flowered, subumbellate in fruit, rachises glabrous or, rarely, sparsely pubescent; fruiting pedicels glabrous or sparsely pubescent.   92 Draba reptans (in part)
       
23 (21) Abaxial surface of leaf blades pubescent, trichomes 3-6-rayed; petals white.   87 Draba praealta (in part)
+ Abaxial surface of leaf blades pubescent, trichomes 2-4-rayed; petals yellow (sometimes fading white)   (24)
       
24 (23) Styles 0.2-0.6(-0.8) mm; fruits 2-3.5 mm wide, valves pubescent, trichomes simple and 2-rayed.   18 Draba brachystylis (in part)
+ Styles 0.01-0.15 mm; fruits 1.3-2.3 mm wide, valves glabrous or pubescent, trichomes simple   (25)
       
25 (24) Cauline leaves 3-10(-17); racemes (15-)20-51(-62)-flowered; fruits lanceolate, 6-9(-11) mm; Arizona, Colorado, New Mexico, Utah.   91 Draba rectifructa
+ Cauline leaves 1 or 2(-4); racemes (2-)4-10(-15)-flowered; fruits usually linear, rarely linear-elliptic, (8-)10-17(-20) mm; Alaska, Alberta, British Columbia, Washington, Yukon.   108 Draba stenoloba (in part)

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