LACTUCA (the old Latin name, from lac, milk; in reference to the milky juice). Lettuce. Including Mulgedium. ORD. Compositae. A genus comprising about sixty species of hardy, and usually weedy, annuals or perennials, natives of the temperate regions of the Northern hemisphere and South Africa, only a few of which are worth growing. Flower-heads blue or yellow; involucre of few bracts, in several series, placed upon a flat, naked receptacle. Fruits somewhat flattened, surmounted by a long, slender beak, and a pappus of long, silky, silvery hairs. Leaves radical or alternate, entire, largely dentate or pinnatifid; margins setose-ciliate or naked. Stems erect, branching. Lactucas thrive in a deep but light or sandy loam, and may be increased by divisions of the roots, or by seeds. All the species of Lactuca abound in a milky juice, which partakes, in a considerable degree, of the qualities of opium. The production of this juice is lessened by culture, and especially by blanching. It is most abundant in plants in a wild state, and in both wild and cultivated Lettuce during inflorescence. It is from the juice of the Lettuce that the late Dr. Duncan, of Edinburgh, prepared the drug called Lactucarium, which is occasionally used as a mild narcotic or sedative where opium is not admissible. See also Lettuce. LACTUCA alpina (alpine).* fl.-heads purplish-blue, large, numerous, disposed in a corymbose cluster. July. l. somewhat lyrate, the terminal lobe triangular and very large. Stems furrowed, erect, smooth below, hairy above. h. 3ft. Arctic and Alpine Europe, West Siberia, and Scotland (but very rare). Perennial. A handsome plant for a somewhat shaded position, in very moist, deep, loamy soil. (Sy. En. B. 809, under name of Mulgedium alpinum.) LACTUCA macrophylla (large-leaved). fl.-heads pinkish-purple, large, corymbose. July. l. radical, large, cordate. Stems stout. h. 4ft. Caucasus. A noble species. LACTUCA macrorhiza (large-rooted).* fl.-heads bright light violet-purple, about 1in. in diameter, and disposed in loose corymbs. Autumn. l. variously formed, sometimes lyrate-pinnatifid, with one or two pairs of lateral lobes, and a large, roundish, terminal one; sometimes very slightly lyrate-pinnatifid, and at other times oblong; those of the stem with broad amplexicaul auricles. h. 6in. to 3ft. Himalayas. Perennial. (B. R. xxxii. 17, under name of Mulgedium macrorhizon.) LACTUCA perennis (perennial). fl.-heads light blue, in corymbose panicles. June to August. l. all pinnatifid; segments linear, toothed upwards. h. 2ft. South Europe, 1596. (B. M. 2130.) LACTUCA Plumieri (Plumier's). fl.-heads purple, disposed in large, spreading, terminal corymbs, with short bracts. Summer. l. broad, large, pinnatifid-runcinate, glaucous underneath. h. 6ft. South of France. A handsome perennial, like LACTUCA alpina, but larger and more ornamental. LACTUCA sativa (cultivated). Common Lettuce. fl.-heads pale yellow, disposed in corymbs on a stem about 3ft. high. June. l. large, roundish or roundish-oblong, entire, slightly toothed, milky. h. 4ft. Generally considered to be a cultivated race derived from LACTUCA Scariola, a widely-distributed weed. Annual. (B. M. Pl. 161.) LACTUCA tuberosa (tuberous).* fl.-heads pale blue, over 1in. across, disposed in loose panicles. Autumn. l. about 1ft. long, 9in. wide, runcinate-pinnatifid, with lanceolate, somewhat recurved, finely-toothed lobes. h. 1ft. to 1 1/2ft. An ornamental perennial, with a neat habit. Tauria.