Lactuca sativa, L.

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1976, Flora Europaea. Volume 4. Plantaginaceae to Compositae (and Rubiaceae), Cambridge University Press : 330

10. L. sativa L. , Sp. Pl. 795 (1753).

Glabrous annual or biennial, with a slender tap-root, dense basal rosette and erect flowering stems 3O-7O(-1OO) cm. Basal leaves undivided or runcinate-pinnatifid, shortly petiolate; cauline simple, ovate to orbicular, cordate-amplexicaul, sessile, not held vertically. Inflorescence a dense, corymbose panicle. Involucre erect in fruit. Capitula numerous, with 7-15(-35) florets. Ligules pale yellow, often violet-streaked. Achenes 6-8 mm; body obovate, often finely muricate at apex, 5- to 9-ribbed, greyish; beak as long as body. 2л = 18. Cultivated as a vegetable almost throughout Europe', frequent as a casual, but seldom naturalized.

Probably originated in Egypt from L. serriola .