18. Draba L. (whitlow wort, whitlow grass)
Plants annual or biennial (perennial or woody elsewhere), terrestrial,
variously pubescent with unbranched to branched and/or stellate hairs. Stems
erect or ascending. Leaves basal and/or alternate, sessile or short-petiolate,
not clasping (clasping elsewhere), simple, the margins entire or shallowly
toothed. Inflorescences racemes, few-branched panicles, rarely appearing nearly
umbellate, the flowers not subtended by bracts (with bracts elsewhere). Sepals
lanceolate to elliptic or ovate, erect or spreading, green. Petals shallowly to
deeply 2-lobed at the tip or unlobed and rounded, white (yellow, lavender, or
purple elsewhere), rarely absent. Styles absent or less than 0.3 mm long (to
17.0 mm elsewhere). Fruits ascending, 2–5 times (to more than 40 times
elsewhere) as long as wide, flattened parallel to the septum (circular in
cross-section elsewhere), dehiscent longitudinally. Seeds in 2 rows in each
locule, 0.5–1.5 mm long (longer elsewhere), ovate to broadly elliptic in
outline, the margins not winged, the surface finely pebbled or warty, sometimes
faintly reticulate, yellow to light orange. About 350 species, nearly
worldwide, except for the Australian region, mostly temperate to arctic.
Draba is the largest genus in the family Brassicaceae. Rollins (1993)
included more than 100 species from North America,
most of these from the western and northern portions of the continent.