Taxonomy

Lactuca serriola L., Cent. Pl. 2. 1756

Common synonyms

Lactuca albicaulis Boiss.; Lactuca altaica Fisch. & C.A.Mey.; Lactuca augustana All.; Lactuca coriacea Sch.Bip.; Lactuca dubia Jord.; Lactuca integrata (Gren. & Godr.) A.Nelson; Lactuca latifolia Gilib.; Lactuca saligna var. robusta Fisch. & C.A.Mey.; Lactuca sativa var. angustana Irish; Lactuca sativa var. angustana Irish ex Bremer; Lactuca sativa var. angustana L. H. Bailey; Lactuca scariola; Lactuca scariola; Lactuca scariola L.; Lactuca scariola f. scariola; Lactuca scariola subsp. augustana (All.) Arcang.; Lactuca scariola subsp. integrata (Gren. & Godr.) Piper; Lactuca scariola subsp. scariola; Lactuca scariola var. augustana (All.) Lindem.; Lactuca scariola var. dubia (Jord.) Rouy; Lactuca scariola var. integrata Gren. & Godr.; Lactuca scariola var. integrifolia (Gray) Bogenh.; Lactuca scariola var. integrifolia Becker; Lactuca scariola var. integrifolia Bisch.; Lactuca scariola var. integrifolia Schur; Lactuca scariola var. scariola; Lactuca scariola var. typica Rouy; Lactuca scariola var. vulgaris Bisch.; Lactuca serriola f. integrifolia (Gray) S.D.Prince & R.N.Carter; Lactuca serriola f. integrifolia Bogenh.; Lactuca serriola subsp. integrifolia (Gray) G.H.Loos; Lactuca serriola subsp. serriola; Lactuca serriola var. integrata (Gren. & Godr.) Beger; Lactuca sylvestris Lam.; Lactuca tephrocarpa K.Koch; Lactuca verticalis Gaterau; Lactuca virosa var. integrifolia Gray; Mycelis muralis f. integrifolia (Beckhaus) Soó

Common name

Prickly lettuce

Description

Propagule or dispersal unit is the fruit with pappus. Fertile part 2-3.5 mm long, 0.8-1.1 mm wide, in side view widest in upper part (obovoid), +/- straight, rarely conspicuously curved, the upper (apical) end narrowing, in cross-section flattened, basal scar (carpopodium) pronounced and well-differentiated, central, beak (=thinner sterile stalk between seed and pappus) present, beak length 3-4.5 mm, wings absent, fruit surface light brown or straw, smooth (except at cellular level), rarely wrinkled, with no hairs (glabrous), thickened margin absent, longitudinal ribs present, 10-18, their surfaces toothed, serrated or scale-like, with no hairs (glabrous) or simple straight hairs.

Pappus type bristles / hairs, pappus elements all +/- similar, up to 3.5-6 mm long, in several rows, pappus elements numerous, falling off as a whole or elements falling off individually, the individual bristles rough / serrated (barbellate), +/- equal width along length, white / translucent.

Notes: The beak breaks easily, so that the pappus will presumably often be missing when this species is encountered. The three species of Lactuca covered in this key have very similar fruits, but L. sativa generally has larger fruits than L. saligna and L. serriola (1-2 mm wide versus up to 1.1 mm wide).