16. Descurainia Webb & Berthel.
Plants annual or biennial (perennials or shrubs elsewhere), terrestrial,
pubescent with short-stalked, branched hairs occasionally mixed with unbranched
hairs and frequently also with stalked glands (less commonly nearly all of the
hairs replaced with stalked glands). Stems erect, usually branched in the upper
half. Leaves alternate and usually also a few basal at maturity,
short-petiolate or sessile, not clasping, the lower leaves ovate to obovate or
oblanceolate in outline, 1–3 times pinnately divided, with toothed,
oblanceolate to linear leaflets and/or divisions, the upper leaves
progressively reduced and less divided, ovate to lanceolate or linear in
outline, 1 time pinnately compound or divided, the leaflets or divisions
linear, toothed. Inflorescences racemes or less commonly panicles, the flowers
often not subtended by bracts. Sepals lanceolate to elliptic or ovate, erect or
ascending, green, often reddish-tinged. Petals not lobed, pale yellow to yellow
or greenish yellow. Styles absent or less than 0.5 mm long. Fruits ascending to
spreading, 4–30 times as long as wide, circular in cross-section or
nearly so, dehiscent longitudinally. Seeds in 1 or 2 rows in each locule,
0.8–1.1 mm long, elliptic to narrowly ovate in outline, the margins not
winged, the surface with a fine, netlike or honeycomb-like pattern of ridges
and pits, orange to reddish brown. About 40 species, North America to South
America, Europe, Asia, Africa.
The seeds of this genus have been used as a substitute for mustard seeds.
Massive ingestion of the plants can poison livestock. The plants also have been
used for various medicinal purposes.