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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 3

1 Basal leaf blade surfaces with malpighiaceous trichomes.   61 Draba malpighiacea
+ Basal leaf blade surfaces with simple, 2-rayed, forked, stellate, or dendritic trichomes   (2)
2 (1) Abaxial surface of leaf blades with some 7-15-rayed trichomes   (3)
+ Abaxial surface of leaf blades with 2-5 (or 6)-rayed trichomes   (11)
3 (2) Petals yellow; stem and basal leaf trichomes crisped.   110 Draba streptobrachia (in part)
+ Petals white or creamy white; stem and basal leaf trichomes usually non-crisped   (4)
4 (3) Margins of basal and cauline leaf blades entire   (5)
+ Margins of basal and, sometimes, cauline leaf blades usually dentate or denticulate, if entire, racemes not flexuous in fruit   (8)
5 (4) Plants usually forming mats; rachises slightly flexuous   (6)
+ Plants not forming mats; rachises not flexuous   (7)
6 (5) Fruits 6-15(-18) mm; adaxial surface of leaf blades with simple and long-stalked, 2-rayed trichomes.   57 Draba lonchocarpa (in part)
+ Fruits 3.5-9 mm; adaxial surface of leaf blades with short-stalked, 8-15-rayed trichomes.   68 Draba nivalis (in part)
7 (5) Rachises pubescent; ovules 22-32 per ovary; sepals persistent (until fruiting); e California, w Nevada.   21 Draba californica (in part)
+ Rachises glabrous; ovules 12-16 per ovary; sepals caducous; Alaska, Alberta, w Montana, nw Wyoming.   86 Draba porsildii (in part)
8 (4) Cauline leaves usually 0, rarely 1 (as a bract); basal leaf blades each with prominent midvein; sepals glabrous or, rarely, with simple trichomes subapically.   55 Draba lactea (in part)
+ Cauline leaves usually 2-25, rarely 1 (D. chamissonis); basal leaf blades each with obscure midvein; sepals with 2-5-rayed trichomes   (9)
9 (8) Fruits 1.1-1.6(-2) mm wide; petals 2-3.5 mm; petiole margins not ciliate; proximalmost flowers bracteate.   24 Draba chamissonis
+ Fruits 2-3.5 mm wide; petals 3.5-5.5 mm; petiole margins ciliate; proximalmost flowers usually ebracteate (sometimes bracteate in D. glabella)   (10)
10 (9) Abaxial surface of leaf blades with sessile, stellate trichomes; styles (0.2-)0.4-1 mm; stems proximally with 8-12-rayed trichomes.   6 Draba arabisans (in part)
+ Abaxial surface of leaf blades with short-stalked, stellate trichomes; styles 0.05-0.2(-0.5) mm; stems proximally with some simple trichomes.   38 Draba glabella (in part)
11 (2) Stem and leaf trichomes sessile, 2 rays parallel to long axis of stem or midvein, some malpighiaceous.   104 Draba spectabilis (in part)
+ Stem and leaf trichomes stalked, rays not parallel to long axis of stem or midvein, not malpighiaceous   (12)
12 (11) Caudex fleshy, simple; petiole of basal leaves (1-)4-15 cm; fruits 4-7(-9) mm wide.   41 Draba grandis
+ Caudex not fleshy, usually branched, rarely simple; petiole of basal leaves obsolete or 1-2 cm; fruits 1-4(-6) mm wide   (13)
13 (12) Abaxial surface of leaf blades with either cruciform or pectinate trichomes   (14)
+ Abaxial surface of leaf blades with cruciform and 2-6-rayed trichomes   (15)
14 (13) Plants pulvinate, caudex densely branched; abaxial surface of leaf blades with pectinate trichomes; ovules 8-16(-20) per ovary.   48 Draba incerta (in part)
+ Plants not pulvinate, caudex loosely branched; abaxial surface of leaf blades with cruciform trichomes; ovules 16-30 per ovary.   52 Draba juvenilis (in part)
15 (13) Seeds 1.8-2.8 × 1.2-2 mm, wing 0.5-1 mm wide; fruits (3.5-)4-6 mm wide.   12 Draba asterophora (in part)
+ Seeds 0.7-1.4(-1.6) × 0.4-0.8(-1) mm, not winged; fruits 1-4(-5) mm wide   (16)
16 (15) Styles (0.6-)0.8-3.6 mm; petals 4-8.5 mm; anthers usually oblong (ovate in D. murrayi)   (17)
+ Styles 0.01-0.6 mm; petals 1.8-4 mm; anthers ovate   (19)
17 (16) Petals white; anthers ovate, 0.4-0.5 mm; fruits 1.5-2 mm wide; styles 0.6-1.5 mm.   66 Draba murrayi
+ Petals yellow; anthers oblong, 0.6-1 mm; fruits 2-5 mm wide; styles (0.8-)1-3.6 mm   (18)
18 (17) Fruits plane; ovules 10-18 per ovary; basal leaf blades (2-) 4-10(-14) mm wide; cauline leaves (3-)5-9(-11); petals 4-6 mm.   1 Draba abajoensis
+ Fruits slightly twisted; ovules 24-36 per ovary; basal leaf blades 7-25(-33) mm wide; cauline leaves 1-3; petals (5-) 6-8.5 mm.   63 Draba mogollonica (in part)
19 (16) Rachises usually glabrous, (rarely sparsely pubescent in D. stenoloba); fruits usually linear, elliptic, or linear-lanceolate, rarely lanceolate, 1-2(-2.5) mm wide; styles 0.01-0.15(-0.2) mm   (20)
+ Rachises pubescent; fruits lanceolate to oblong or ovoid, (1.8-) 2-4 mm wide; styles 0.1-0.6 mm   (22)
20 (19) Sepals pubescent, trichomes simple and 2- or 3-rayed; abaxial surface of leaf blades with trichomes (2-)4(-6)-rayed.   78 Draba paucifructa (in part)
+ Sepals glabrous or sparsely pubescent, trichomes simple; abaxial surface of leaf blades with trichomes 2-4-rayed   (21)
21 (20) 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)
22 (19) Petals yellow; fruits ovoid to ovoid-lanceolate, inflated (at least basally); ovules (4-)8-12 per ovary.   103 Draba sobolifera (in part)
+ Petals white or creamy white; fruits oblong, lanceolate, or lanceolate-elliptic, flattened; ovules 18-32 per ovary   (23)
23 (22) Fruiting pedicels pubescent, trichomes 4-8-rayed; sepals persistent; petals 0.8-1 mm wide; e California, w Nevada.   21 Draba californica (in part)
+ Fruiting pedicels pubescent, trichomes simple and 2-4-rayed; sepals caducous; petals 1.7-2.5 mm wide; Canada, Greenland.   69 Draba norvegica (in part)

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