1	Fruit echinulate		(2)
+	Fruit not echinulate		(5)
2 (1)	The spines of the fruit oriented almost parallel to the surface of the disc		Medicago polymorpha
+	The spines of the fruit oriented almost at right angles to the surface of the disc		(3)
3 (2)	Leaflets cuneate, usually pubescent on the lower surface only, spines of the fruit inserted very near the dorsal suture		(4)
+	Leaflets obovate, rarely oblanceolate, pubescent on both surfaces, spines of the fruit not inserted very near the dorsal suture		Medicago minima
4 (3)	Fruit spherical or ovoid with 5-7 coils, individual fruits sometimes with fewer coils; peduncle longer than the petiole		Medicago laciniata var. laciniata
+	Fruit cylindrical, with 2½-4½ coils; peduncle shorter than the petiole		Medicago laciniata var. brachycantha
5 (1)	Fruit forming more than 1 spiral		(6)
+	Fruit not forming more than 1 spiral		(7)
6 (5)	Fruit 4-5 mm broad, glabrous		Medicago orbicularis
+	Fruit 2 mm or less broad, glabrous to pubescent		Medicago sativa
7 (5)	Fruit 3 mm or less long		Medicago lupulina
+	Fruit 8-11 mm long, curved		(8)
8 (7)	Curvature of the fruit making a semicircle		Medicago falcata
+	Curvature of the fruit more pronounced than a semicircle		Medicago x varia