Lactuca L.
Annual to perennial taprooted or rhizomatous herbs. Hairs bristly, spinous, or 0. Stems usually branching above. Lvs basal and cauline, pinnatifid to entire. Infl. a diffuse panicle, or spicate with capitula sessile in axillary clusters. Involucral bracts glabrous; outer bracts small; inner bracts becoming larger, not in distinct rows. Receptacle pitted, without scales or hairs. Corolla ligulate, yellow. Achenes pale or dark, 5-35, flattened, usually ribbed; beak paler than achene or concolorous; pappus bristles in 2 rows of equal length, white, > achene body, simple, free to base.
Key
1
Upper cauline lvs usually linear-hastate, sometimes pinnatifid with linear lobes; margins smooth; infl. spicate
Upper cauline lvs obovate, ovate, or subulate-amplexicaul, pinnatifid with oblong or obovate lobes or not lobed; margins toothed; infl. diffuse, paniculate
3
Lateral lobes of basal lvs about as wide as the sinus between them; achenes pale, sometimes greyish or dark-spotted; achene body 2.5-3 mm long; involucre 8-13 mm long
Lateral lobes of basal lvs wider than the sinus between them; achenes very dark brown or black; achene body 4-5 mm long; involucre (11)-13-15 mm long
100 spp., Eurasia, Africa. Naturalised spp. 4.
