=Description.=—The rather stiff, dark-green, branching stem of black mustard is from 4 to 6 feet in height. The lower part of the stems and branches is more or less bristly hairy, but the upper part is usually smooth. The leaves are dark green, somewhat rough, with bristly hairs, and are all borne on stalks. The lower leaves are lobed, the terminal lobe being the largest and the two or more lateral ones smaller. The leaves toward the top of the plant become lance shaped and are slightly toothed. The flowers of black mustard appear from June to September, and are of a bright yellow color. They are rather small, scarcely a quarter of an inch in diameter, the four petals spreading and each consisting of a rounded blade with a narrow claw. The petals alternate with the pale-green sepals or calyx lobes. The flowers appear in clusters at the ends of the elongating stems, followed from July to November by the numerous erect pods crowded against the stem in dense narrow clusters. The pods are about 1 inch in length, quadrangular, smooth, and tipped at the apex by the short, persistent style. The seeds contained in the pods are very numerous, small, about one twenty-fifth of an inch in diameter, globular, blackish brown, and finely pitted. The plant is an annual, and if care is taken to prevent the distribution of the seeds it is not difficult to exterminate. The seeds possess great vitality, and may remain in the ground for years before germinating. =Collection of seeds.=—The tops may be pulled when most of the pods are nearly mature, but before they are ready to spring open. They should then be placed on a clean, dry floor or shelf, allowing the pods to ripen and dry out, when they will burst open and the seeds can be readily shaken out. Mustard seed has no odor whatever when collected, not even when it is powdered in its dry state, but as soon as water is added in grinding it, the powerful, penetrating mustard odor is developed. The taste is sharp and pungent. WHITE MUSTARD. _Sinapis alba_ L. =Another common name.=—Yellow mustard. (Fig. 31.) [Illustration: FIG. 31.—White mustard (_Sinapis alba_ L.).] =Range and habitat.=—White mustard is a weed found in cultivated land along waysides and fence rows, but is not so abundant nor so widely distributed as the black mustard. It is naturalized in this country from Europe. =Description.=—This plant is very similar to black mustard, but is smaller (growing only about 1 to 2 feet tall), bright green, but the flowers and seeds are much larger, and the rough-hairy pods with their long, sickle-shaped beaks are spreading instead of being pressed against the stem. The flowers are paler yellow than those of the fore-going species. The divisions of the leaves reach to the midrib, the leaves are rough-hairy, and the pods bristly. The seeds are pale yellow and smooth.