Lactuca

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

Sect. Lactuca . Inflorescence a dense panicle of many capitula. Capitula with 10-50 florets. Achenes elliptical to obovate, 1 - to 9-ribbed, narrowed in the upper part, with distinct, slender, pale beak usually at least as long as body.