One of the commonest of these is the Wild Mustard or Charlock (_Brassica arvensis_ or _B. Sinapis_), a very abundant weed in most cultivated fields, probably introduced originally from South Europe. It is a very coarse plant, with scattered, bristly, spreading hairs, growing from one to two feet high, and bearing racemes of yellow flowers that generally exceed a diameter of half an inch. The leaves are ovate, with short, stiff hairs; all are pinnately lobed, and the lower ones have generally a large oval lobe, with coarsely-toothed segments, and a few narrower segments along the stalk. The fruits are spreading, many-angled pods, usually about an inch in length, constricted between the seeds when ripe, with a beak about a third the length of the whole pod enclosing a single seed at its base. The plant flowers from May to August. The White Mustard (_Brassica alba_ or _Sinapis alba_) is not so common; but it is somewhat largely cultivated for its seedlings, which are used, with those of cress, as salad; and the plant is not unfrequently found as a weed in corn-fields and on other cultivated ground. The whole plant is clothed with rather stiff hairs that are directed downwards, and its height varies from one to two feet. Its leaves are pinnately divided into ovate, coarsely-toothed segments, the terminal one largest. The flowers are bright yellow, about half an inch in diameter, in racemes. The pods are usually near an inch long, on spreading stalks; with a stout, flattened beak, longer than the pod itself, containing a single seed. They are constricted between the seeds, and both valves and beak are clothed with stiff, whitish hairs. The plant flowers during June and July. [Illustration: THE FUMITORY.] A third member of the same genus--the Black Mustard (_Brassica nigra_ or _Sinapis nigra_)--is also cultivated for its seeds, which are used in the preparation of table mustard, and it is also a moderately common weed of cultivation in many parts. It is a hairy plant, from one to three feet high. Its lower leaves are rough, and deeply divided into a large terminal and small lateral lobes; and the upper ones are small, very narrow, smooth and undivided. The flowers are yellow, usually less than half an inch across, in long, narrow racemes; and the shortly-stalked pods are four-angled, smooth, and about half an inch long. They do not spread much, and the short beak consists only of the narrow style. This species flowers from June to August. [Illustration: THE BLACK MUSTARD.]