16. Plants annual or perennial; stems prostrate to weakly ascending (often 



acaulescent), if stiffly erect and more than 3 dm. tall then the 

 legume inflated and less than 6 times as long as broad (18) 



17(16). Grayish-pubescent erect subshrubs, not climbing 10. Indigofera 



17. Not grayish-pubescent, high-climbing vine 21. Apios 



18(16). Peduncle of mature flowering racemes 8-30 cm. long 13. Astragalus 



18. Peduncle of flowering racemes 1-8 (-9) cm. long (19) 



19(18). Flowers when fresh brick-red or reddish (often fading to lavender 

 when in dried specimens); perennials 10. Indigofera 



19. Flowers of various colors but not brick-red or reddish; annuals or perennials 



(20) 



20(19). Keel petals acute, blunt or rounded apically 13. Astragalus 



20. Keel petals with the apex extending into a sharp erect point; plants acaules- 



cent; flowers purple or pinkish-purple 14. Oxytropis 



21(7). Leaves gland-dotted 11. Amorpha 



21. Leaves not gland-dotted (22) 



22(21). Rachis of leaf 1-8 cm. long; legume 15-35 mm. long; flowers 5-10 mm. 

 long 10. Indigofera 



22. Rachis of leaf 8 cm. long or more; legume 30 mm. long or more; flowers 



10 mm. long or more 12. Sesbania 



23(6). Leaves with tendrils 20. Lathyrus 



23. Leaves without tendrils (24) 



24(23). Twining vines (often trailing when support is lacking) 22. Vigna 



24. Herbs or shrubs with erect or trailing stems, never twining (25) 



25(24). Leaflets dentate or denticulate at least near the apex (sometimes min- 

 utely so) (26) 



25. Leaflets entire, not at all toothed (28) 



26(25). Flowers in slender elongate racemes at least 4 to 8 times as long as 

 thick 7. Melilotus 



26. Flowers in short thick racemes or umbels 3 times as long as thick or 



shorter (27) 



27(26). Fruit coiled or curved, longer than the calyx; leaves trifoliolate, not 

 palmate 6. Medicago 



11. Fruit not coiled nor curved, shorter than the calyx; leaves usually palmate 

 8. Trifolium 



28(25). Leaves (or at least some of them) with petioles 15 mm. long or more 

 18. Lespedeza 



28. Leaves with petioles less than 14 mm. long (29) 



29(28). Stipules minute, reduced to glands; fruit several-seeded 9. Lotus 



29. Stipules not reduced to glands; fruit 1-seeded 18. Lespedeza 



1. Mimosa L. Mimosa. Catclaw 



Shrubs or lianes or (in 1 species) prostrate perennial herbs, in most species 

 the herbage and even the legumes armed with scattered recurved prickles; leaves 

 pinnately twice-compound with 1 to 14 pairs of pinnae; leaflets few to numerous; 

 stipules usually small and subulate, never spinescent; flowers small and aggregated 

 into white, pink to reddish globes or rarely short spikes; stamens 8 to 10 

 (usually exactly twice as many as petals), usually colored, free above the floral 

 cup; fruit a flattened (sometimes contorted) pod usually a few cm. long, with 



1041 



