38. Sinapis L. (charlock)

Plants annual, terrestrial, usually with unbranched, frequently coarse, spreading or recurved hairs, sometimes nearly glabrous above. Stems erect, usually branched. Leaves alternate and basal, the lower leaves usually with petioles, the upper leaves progressively reduced and short-petiolate or sessile, the bases not clasping. Inflorescences panicles or racemes, the lower branches subtended by reduced leaves, the flowers bractless. Sepals spreading or reflexed, narrowly oblong to linear. Petals unlobed, yellow, without conspicuously darkened veins. Fruits 20–45 mm long, mostly more than 10 times as long as wide, spreading or ascending, straight or slightly arched upward, circular or slightly 4-angled in cross-section, prominently beaked with a distinct, conical or flattened, often seedless area in addition to the style, the portion below the beak dehiscing longitudinally, each valve with 3–7 distinct nerves. Seeds in 1 row in each locule, globose. Seven species, native to Europe, Asia, Africa.

Some North American botanists have treated Sinapis as part of Brassica (Steyermark, 1963), although most European authorities have maintained these groups as separate genera. The two seem quite distinct. The sepals of Brassica species are erect and somewhat pouched at the base (saccate), whereas those of Sinapis species are spreading to reflexed and not concave. The beaks of the fruits of Sinapis species are far more strongly differentiated from the lower portions than in Brassica species, and the valves of the lower portions have more veins. The chemistry of the mustard oils and seed proteins in the two groups also is different (Al-Shehbaz, 1985).