B. (or Sinàpis) álba. (White Mustard.) Pods bristly, ascending on spreading pedicels, more than half its length occupied by the sword-shaped 1-seeded beak; leaves all pinnatifid; seeds pale. (Cult. and adv. from Eu.)
B. (or Sinàpis) nìgra, Koch. (Black Mustard.) Pods smooth (½´ long), 4-cornered (the valves only 1-nerved), erect on appressed pedicels forming a slender raceme, tipped with a stout persistent style; seeds dark brown, smaller and more pungent than in the last; lower leaves with a large terminal lobe and a few small lateral ones.—Fields and waste places. (Adv. from Eu.)
B. campéstris, L., in the form of the Rutabaga and the Turnip, sometimes persists a year or two in neglected grounds.
18. CAPSÉLLA, Medic. Shepherd's Purse.
Pod obcordate-triangular, flattened contrary to the narrow partition; the valves boat-shaped, wingless. Seeds numerous. Cotyledons incumbent.—Annuals; flowers small, white. (Name a diminutive of capsa, a box.)
C. Bursa-pastòris, Moench. Root-leaves clustered, pinnatifid or toothed; stem-leaves arrow-shaped, sessile.—Waste places; the commonest of weeds. April–Sept. (Nat. from Eu.)
19. THLÁSPI, Tourn. Pennycress.
Pod orbicular, obovate, or obcordate, flattened contrary to the narrow partition, the midrib or keel of the boat-shaped valves extended into a wing. Seeds 2–8 in each cell. Cotyledons accumbent. Petals equal.—Low plants, with root-leaves undivided, stem-leaves arrow-shaped and clasping, and small white or purplish flowers. (Ancient Greek name, from θλάω, to crush, from the flattened pod.)
T. arvénse, L. (Field P. or Mithridate Mustard.) A smooth annual, with broadly winged pod ½´ in diameter, several seeded, deeply notched at top; style minute.—Waste places; rarely naturalized. (Nat. from Eu.)
20. LEPÍDIUM, Tourn. Pepperwort. Peppergrass.