Description
Key Characters:
Growth Form:
Erect annual herbs 5–25 dm tall, branched above, with watery and usually pungent sap.
Stems:
Stems sparsely hirsute, especially on lower parts of stem, or subglabrous.
Roots:
Leaves:
Leaves simple.
Alternate or rarely opposite.
Lower blades deeply pinnatified, with a large terminal lobe and a few small lateral ones, 10–20 cm long, 3–9 cm wide. cauline leaves gradually reduced.
Cauline leaves sessile, not clasping the stem.
Stipules absent.
Flowers:
Flowers in usually bractless, in elongate, terminal racemes.
Flowers bisexual (perfect), actinomorphic or rarely slightly irregular; showy.
Calyx of 4 sepals, ascending or spreading, deciduous, erect, usually oblong, inner ones ± gibbous at base.
Corolla of 4 petals, rarely absent, yellow, 7–8 mm long, long–clawed.
Stamens (2–4)6(–16), tetradynamous, the inner 4 usually in pairs, sometimes connate at base in pairs; anthers dithecal, opening by longitudinal slits.
Ovary superior, 2(4?)-carpellate, usually 2-celled by means of a false, but usually complete septum, rarely 1-celled, sessile or rarely stipitate; ovules 1 to numerous, borne on parietal placentas on replum margin at periphery of ovary wall, campylotropous or occasionally anatropous; style 1 or occasionally absent; stigma truncate or 2-lobed.
Fruit:
Capsules divided into 2 cells by the usually thin and membranous septum; elongate (at least 3 times as long as wide) and referred to as a silique. fruit an elongate; linear silique; often torulose; terete (cylindrical) or 4–angled; with a stout; indehiscent; flat or conical; often 1–seeded beak. Siliques erect; appressed to the stem; 1–2 cm long; the beak sterile; 1–4 mm long.
Seeds 1 to numerous; often becoming mucilaginous when wet; endosperm essentially absent. Seeds dark reddish brown; globose; 1–1.3 mm in diameter; the surface finely reticulate.
Ploidy:
2n = 16; 32
Habitat:
Naturalized in disturbed areas; especially along roadsides and in pastures.
Elevation Range: