Lettuce (Lactuca), a genus of Compositac, represented by several British species and one of unknown origin commonly cultivated as L. sativa. It probably came from Asia, and has been grown in England since 1562, Gerard describing eight varieties as early as 1597. It is an annual, with roundish or obovate-obtuse leaves, entire or slightly-toothed, and varying in colour. The flower stem is erect, branching, and about 3 feet high; the involucre consists of a few overlapping bracts; the receptacle is naked; the florets are all ligulate and pale yellow, and the fruits are flattened and have a stipitate pappus. The cultivated forms are grouped as either cabbage lettuces, with compact heads and rounded leaves, or cos lettuces, with longer, upright, firmer leaves. They are not nutritious, but pleasantly cooling as salad. When flowering the plant produces more of the milky, bitter, and slightly narcotic sap from which the mild opiate Lactucarium is prepared. Venus mourning Adonis is said to have soothed herself on a bed of lettuces; Herodotus mentions them as served at the Persian Court 400 years B.C.; Virgil and Columella recommend them as salad; Augustus is said by Pliny to have been cured of an illness by eating them freely; and Galen is said to have used them as an opiate in the 3rd century A.D.