1. Fruit, even when immature, covered with hooked spines; stipules deeply toothed or lacerate.
2. Stem glabrous or nearly so; fruit glabrous between the spines.
2. Stem densely pubescent; fruit ± pubescent between the spines and weakly glandular on the surface.
1. Fruit without spines; stipules at most shallowly toothed.
3. Corolla 1.8–2.2 (–2.5) mm long, yellow; plant low and ± prostrate or slightly ascending; fruit ± reniform, 1-seeded, nearly black when mature.
3. Corolla (7–) 8–10 (–11) mm long, blue-purple or (less often) yellow, cream, or variegated (white in albinos); plant erect; fruit curved to spirally coiled, several-seeded, green when mature.
All species found in Medicago
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. June 21, 2018. https://www.michiganflora.net/genus.aspx?id=Medicago.