2. Descurainia sophia (L.) Webb ex Prantl (flixweed, tansy mustard)

Pl. 319 f–g; Map 1342

Stems (10–)25–80(–100) cm long, moderately to usually densely pubescent with many-branched, nonglandular hairs. Leaves 1–15 cm long, moderately to usually densely pubescent with many-branched hairs, 2 or 3 times pinnately dissected. Sepals 2.0–2.5 mm long. Petals 2.0–2.5 mm long, yellow. Fruits linear, (12–)15–25(–30) mm long, 0.5–1.2 mm wide, tapered and pointed at the tip, the valves with a prominent midnerve, the septum with 2 or 3 longitudinal veins, the fruits and their stalks ascending. Styles absent to 0.2 mm. Seeds 20–40 per fruit, in 1 row in each locule. 2n=20, 28, 38. May–July.

Introduced, uncommon and widely scattered in Missouri (native of Europe, Asia, widely introduced in the U.S., Canada). Railroads, roadsides, and open, disturbed areas.