1	Cauline leaves sessile, amplexicaul, sagittate, or auriculate at base.		(2)
+	Cauline leaves petiolate or subsessile, cuneate or obtuse at base, if subauriculate then plants with capitate or clavate papillae.		(5)
2 (1)	Flowers yellow; upper leaves amplexicaul-perfoliate, basal leaves 2- or 3-pinnatisect; seeds winged all around		10 L. perfoliatum
+	Flowers white; upper leaves auriculate or sagittate, basal leaves entire, dentate, or pinnatifid; seeds wingless.		(3)
3 (2)	Annuals or biennials, usually densely long pubescent; fruit wings united with lower part of style; leaves herbaceous		1 L. campestre
+	Perennials, glabrous, papillate, or crisped hairy; fruit wings free from style; leaves leathery.		(4)
4 (3)	Basal and lowermost cauline leaves pinnatifid, upper ones subentire; plants glabrous		3 L. cordatum
+	All leaves entire; plants with curved papillate trichomes		4 L. cartilagineum
5 (1)	Stamens 6; stems glabrous or pubescent with long trichomes (puberulent in L. alashanicum).		(6)
+	Stamens 4 or 2; stems puberulent with clavate or capitate papillae, sometimes with minute trichomes.		(11)
6 (5)	Petals absent; plants puberulent with subclavate papillate trichomes; all leaves linear, entire, margin involute		9 L. alashanicum
+	Petals well developed; plants glabrous or pilose with slender trichomes; leaves variously-shaped, at least some pinnatifid, pinnatisect, dentate, or serrate, margin flat.		(7)
7 (6)	Annuals; fruit (4-)5-6 mm, winged all around, broadly so apically; all or at least lower leaves 1- or 2-pinnatisect or -pinnatifid; cotyledons 3-lobed		2 L. sativum
+	Perennials; fruit 1.5-3 mm, wingless or only apically winged; leaves entire, serrate, or dentate; cotyledons entire.		(8)
8 (7)	Sepals persistent in fruit; fruit cordate at base		7 L. obtusum
+	Sepals deciduous shortly after anthesis; fruit cuneate, obtuse, or rounded at base.		(9)
9 (8)	Basal and lowermost cauline leaves pinnatifid or lyrate, with oblong or linear lateral lobes much smaller than terminal one; style (0.2-)0.3-0.4(-0.5) mm, distinctly exserted from apical notch		8 L. lacerum
+	Basal and lowermost leaves dentate, serrate, or subentire; style absent, obsolete, or rarely to 0.1 mm.		(10)
10 (9)	Uppermost cauline leaves sessile or subsessile, leathery; fruit not carinate; seeds (0.8-)1-1.3 mm		6 L. latifolium
+	Uppermost cauline leaves shortly petiolate, papery; fruit carinate; seeds 1.5-2.2 mm		5 L. ferganense
11 (5)	Stamens 4; style longer than and exserted from apical notch of fruit		11 L. cuneiforme
+	Stamens 2; style shorter than and included within apical notch of fruit.		(12)
12 (11)	Fruit orbicular; upper stems and rachis puberulent with curved minute trichomes; cotyledons accumbent		13 L. virginicum
+	Fruit elliptic, ovate, or obovate; upper stems and rachis puberulent with straight or clavate papillae; cotyledon incumbent.		(13)
13 (12)	Middle and upper cauline leaves usually pinnatifid; infructescences capitate; petals 0.5-1 mm		12 L. capitatum
+	Middle and upper cauline leaves dentate, serrate, or entire; infructescences elongated racemes; petals absent or rudimentary.		(14)
14 (13)	Basal leaves 2- or 3-pinnatisect; pedicels puberulent all around with slender trichomes; herbs fetid		14 L. ruderale
+	Basal leaves 1-pinnatifid or serrate; pedicel papillate only adaxially; herbs not fetid.		(15)
15 (14)	Fruit broadly obovate, widest above middle; raceme papillae terete or subclavate		15 L. densiflorum
+	Fruit elliptic, widest at middle; raceme papillae clavate or capitate		16 L. apetalum