60 



22a. Leaflets 5; flowers rose-purple in a spike-like head (5 8 

 dm. high, late summer) 



Prairie Clover, Petalostemum purpureum. 

 22b. Leaflets more than 5 23. 



23a. Flowers bright-blue, in a dense spike (3 6 dm. high; sum- 

 mer) 8a. 



23b. Flowers bright-yellow; stamens not united (summer) 24. 

 23c. Flowers white, cream-color, or yellowish, or marked with pur- 

 ple 26. 

 24a. Leaflets linear-oblong, 2 cm. long or less; stamens 5 or 10 



(36 dm. high) (Partridge Pea) 25. 



24b. Leaflets lanceolate-oblong, 2 5 cm. long; 7 stamens with 

 normal anthers and 3 with imperfect anthers (8 15 dm. high) 



Wild Senna, Cassia marilandica. 

 25a. Anthers 10; flowers 2 4 cm. wide 



Partridge Pea, Cassia chamaecrista. 

 25b. Anthers 5; flowers 5 10 mm. wide 



Partridge Pea, Cassia nictitans. 



26a. Silky-hairy with whitish hairs; flowers marked with pur- 

 ple (3 5 dm. high; summer) Goat's Rue, Tephrosia virginiana. 

 26b. Glabrous or nearly so (summer) (Milk Vetch) 27. 



27a. Flowers greenish cream-color (4 10 dm. high) 



Milk Vetch, Astragalus canadensis. 

 27b. Flowers white (35 dm. high) 



Milk Vetch, Astragalus neglectus. 



28a. Flowers in heads, umbels, or short dense spikes 29. 

 28b. Flowers in loose racemes or panicles 42. 

 29a. Flowers bright-yellow; decumbent or ascending plants (spring 



and summer) 30. 



29b. Flowers white, cream, purple, or red; never yellow 34. 

 30a. Whole flower only about 2 mm. long; pod coiled 31. 

 30b. Flowers larger, each one 3 6 mm. long; pod straight (1 4 



dm. high) (Hop Clover) 32. 

 31a. Flowers numerous in each head 



Black Medick, Medicago lupulina, 

 31b. Flowers in clusters of 2 20 Bur Clover, Medicago hispida. 



32a. Stipules linear Hop Clover, Trifolium agrarium. 



32b. Stipules ovate 33. 



33a. Heads densely flowered; flowers 20 or more; upper petal striate 

 when dry Hop Clover, Trifolium procumbens. 



33b. Heads loosely flowered; flowers usually 10 or fewer; upper 

 petal scarcely striate or not at all 



Hop Clover, Trifolium dubium. 



34a. Leaves palmately compound, the 3 leaflets all from the 

 same point (late spring and summer) (Clover) 35. 



34b. Leaves pinnately compound, the terminal leaflet on a dis- 

 tinct stalk 39. 



