B. nigra bears yellow flowers in slender racemes. Leaves, the lower ones lyrate, the terminal lobe being large and often divided. Pods, 1/2 inch long, filled with dark-colored, pungent seeds. Plant, 3 to 6 feet high, much branched.

Table mustard is made from the seeds of white and black mustard. When powdered and mixed with warm water the most pungent oil known is generated, causing strangulation if breathed. In England mustard is sown for forage. It is cut before the seeds are ripe and fed to cattle. The oil of mustard is used in making soap. Sinapis (common mustard) was known to the Greeks and Romans 300 years before Christ. The mustard referred to in Scripture is thought to be a small tree allied to the olive, whose fruit tastes like mustard-seed. Cabbage and turnip belong to this genus.