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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 2

1 Plants stoloniferous; basal leaves not rosulate (subopposite).   72 Draba ogilviensis (in part)
+ Plants not stoloniferous (usually cespitose); basal leaves rosulate   (2)
2 (1) Abaxial surface of leaf blades glabrous   (3)
+ Abaxial surface of leaf blades pubescent   (9)
3 (2) Fruit valves pubescent, trichomes simple and 2-4-rayed; styles (0.7-)1.6-3 mm; petals 5.5-8 mm; n California and s Oregon.   46 Draba howellii (in part)
+ Fruit valves glabrous or puberulent, trichomes simple; styles 0.02-1.2(-1.8) mm; petals 1.5-5(-6) mm; not California nor Oregon   (4)
4 (3) Racemes bracteate; basal leaf blades linear to linear-oblanceolate.   40 Draba graminea
+ Racemes ebracteate; basal leaf blades usually obovate to oblanceolate, rarely linear-lanceolate   (5)
5 (4) Cauline leaves 1; fruits plane; styles 0.02-0.4(-0.6) mm   (6)
+ Cauline leaves (1 or) 2-8; fruits slightly twisted or plane; styles (0.4-) 0.7-1.2(-1.8) mm   (7)
6 (5) Petals yellow (often fading white), oblanceolate, 1.5-2.5(-3) × 0.5-1 mm; stems glabrous or with simple trichomes; styles 0.02-0.1 mm.   29 Draba crassifolia (in part)
+ Petals white, obovate, 3-5 × 1.8-3 mm; stems glabrous or with 2-8-rayed trichomes; styles 0.1-0.4(-0.6) mm.   55 Draba lactea (in part)
7 (5) Basal leaves undifferentiated into blade and petiole, 0.5-0.8 cm, persisting as a whole, imbricate, blade margins with setiform trichomes.   43 Draba heilii (in part)
+ Basal leaves differentiated into blade and petiole, 1.2-8.5 cm, petiole persisting, not imbricate, blade margins without setiform trichomes   (8)
8 (7) Fruits lanceolate to ovate-lanceolate, (7-)8-14 × 3-5 mm; rachises pubescent (trichomes crisped); Colorado, Montana, Utah Wyoming.   28 Draba crassa
+ Fruits linear-elliptic to elliptic, 5-10(-13) × 1.5-2.5 mm; rachises usually glabrous, rarely pubescent (trichomes non-crisped); se Arizona, s New Mexico, w Texas.   107 Draba standleyi (in part)
9 (2) Fruit valves pubescent, trichomes 2-12-rayed   (10)
+ Fruit valves glabrous, pubescent, or puberulent, trichomes simple   (13)
10 (9) Styles 1.4-3.4 mm; cauline leaves (4-)6-10(-13); racemes (10-)18-55(-67)- flowered; petals yellow, linear.   26 Draba corrugata (in part)
+ Styles 0.1-0.8 mm; cauline leaves 1-3; racemes 2-20-flowered; petals white, spatulate to obovate   (11)
11 (10) Fruits 2-5 × 1.5-2 mm; ovules 36-52 per ovary; petals 1.5-2 × 0.7-0.8 mm.   120 Draba yukonensis
+ Fruits 4-9.5 × 2-4 mm; ovules 20-36 per ovary; petals 3-5 × 1.5-2.5 mm   (12)
12 (11) Fruits with 2-4-rayed and, sometimes, fewer, 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)
13 (9) Styles (0.7-)1-3 mm; fruits usually twisted, rarely plane; petals (4-)4.5-7.5 mm   (14)
+ Styles 0.01-1(-1.2) mm; fruits not or, rarely, slightly twisted; petals 1.5-4(-4.5) mm   (17)
14 (13) Cauline leaf blade margins dentate; fruiting pedicels horizontal to divaricate; se Arizona.   15 Draba bifurcata (in part)
+ Cauline leaf blade margins entire; fruiting pedicels usually ascending, rarely divaricate-ascending; Arizona, Colorado, New Mexico, Texas, Wyoming   (15)
15 (14) Fruits usually twisted (to 3 turns), rarely plane; stems proximally with trichomes 0.4-2.2 mm; ovules 20-34 per ovary; c Colorado, n New Mexico, se Wyoming.   111 Draba streptocarpa
+ Fruits usually twisted (to 1 turn), rarely plane; stems proximally with trichomes 0.1-0.7 mm; ovules 12-24 per ovary; se Arizona, s New Mexico, w Texas   (16)
16 (15) Basal leaves undifferentiated into blade and petiole, 0.5-0.8 cm, persisting as a whole, imbricate, blade margins with setiform trichomes.   43 Draba heilii (in part)
+ Basal leaves differentiated into blade and petiole, 1.2-8.5 cm, petiole persisting, not imbricate, blade margins without setiform trichomes.   107 Draba standleyi (in part)
17 (13) Annuals, biennials, or perennials (not cespitose); fruiting pedicels (3-)5-14 (-16) mm   (18)
+ Perennials (cespitose); fruiting pedicels 1-6 mm   (19)
18 (17) Abaxial surface of leaf blades pubescent with 2-4-rayed trichomes; stems pubescent, trichomes simple and 2-rayed.   2 Draba albertina (in part)
+ Abaxial surface of leaf blades glabrous or with some simple and 2-rayed trichomes; stems usually glabrous, rarely pubescent basally, trichomes simple.   29 Draba crassifolia (in part)
19 (17) Petals yellow, 1-2 mm wide; styles (0.2-)0.3-1.2 mm   (20)
+ Petals white, 0.4-1(-1.5) mm wide; styles 0.05-0.2(-0.3) mm   (22)
20 (19) Abaxial surface of leaf blades with sessile or subsessile, appressed, 2-4-rayed trichomes; fruits ovate, 4-8 mm; styles 0.2-0.3 mm.   119 Draba weberi
+ Abaxial surface of leaf blades with stalked 2- or 3-rayed trichomes; fruits lanceolate to oblong-lanceolate, 4-13 mm; styles 0.3-1.2 mm   (21)
21 (20) Petals 2-2.5(-3) mm, erect, not clawed; anthers oblong, 0.6-0.9 mm; fruits plane; rachises usually glabrous, rarely sparsely pubescent.   36 Draba exunguiculata
+ Petals 3-4.5 mm, not erect (flared, clawed); anthers ovate, 0.3-0.5 mm; fruits twisted or plane; rachises pubescent.   42 Draba grayana
22 (19) Fruit valves glabrous; stems glabrous or, rarely, sparsely pubescent (trichomes straight); petals 2-3.5 × 0.8-1.5 mm.   37 Draba fladnizensis (in part)
+ Fruit valves usually pubescent, rarely glabrous; stems pubescent (trichomes crisped); petals 1.5-2 × 0.4-0.8 mm   (23)
23 (22) Racemes 2-7-flowered, rachises glabrous; sepals caducous; fruits lanceolate, flattened; Yukon.   54 Draba kluanei
+ Racemes (3-)6-13(-17)-flowered, rachises pubescent or, rarely, glabrous; sepals persistent; fruits ovoid to subellipsoid, slightly inflated basally; e California.   64 Draba monoensis (in part)

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