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).