860 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Plants decumbent to prostrate; pods 3 mm. in diameter, 



oblong, about 1 cm. long 35. A. flexuosus. 



Pods membranous to woody, more or less inflated, not terete nor 

 flattened laterally. 

 Pods membranous, strongly inflated. 

 Plants with only a few leaves; pods mottled. 



38. A. ceramicus. 

 Plants with many leaves. 



Pods small, about 1 cm. in diameter, spherical; plants about 



40 cm. high 39. A. ihurbcri. 



Pods larger, more than 1 cm. in diameter, elliptic to lunate 

 in vertical section; plants variable in size. 



Annual; flowers reddish purple, small 40. A. wootoni. 



Perennials; flowers various. 

 Pods almost lunate in cross section, the upper suture 

 nearly straight or slightly recurved. 



41. A. allochrous. 

 Pods elliptic, the upper suture curved about as much as 



the lower, slightly inflexed 42. A. subcinereus. 



Pods only slightly inflated, the walls thick, subcoriaceous to 

 woody. 

 Pods subcoriaceous to chartaceous. 

 Plants acaulescent, small. 

 Flowers capitate, on conspicuous peduncles; pods about 



5 mm. long 43. A. gilensis. 



Flowers (few) racemose, on very short peduncles; pods 



20 mm. long or more 44. A. elatiocarpus. 



Plants with stems over 10 cm. long. 



Plants prostrate, trailing. (Lower suture sometimes in- 

 troverted.) 



Leaflets pubescent on both surfaces 45. A. sonorae. 



Leaflets glabrous on the upper surface. 



54. A. hosackiae. 

 Plants erect or spreading. 



Pod short-stipitate, ellipsoidal, the upper suture curved 



downward 46. A. greenei. 



Pods sessile, sublimate (acuminate), the upper suture 



straight or slightly recurved 47. A. gertrudis. 



Pods coriaceous to woody when mature, thick-walled or fleshy 

 when young. 

 Leaflets ovate-lanceolate, acute, numerous; peduncles 



about 20 cm. long 48. A. neomcxicanus. 



Leaflets oblong to obovate, obtuse, few; peduncles shorter, 

 less than 20 cm. long. 

 Flowers small, 10 mm. long or less; pods of about the 



same length; stems usually short 49. A. tcphrodes. 



Flowers larger, 12 to 15 mm. long; pods 15 to 20 mm. long; 

 Btems frequently 20 cm. long 50. A.remulcus. 



No. 51, Astragalus albulus, is omitted from the key, because without mature fruit 

 it is impossible to place it in any of the sections, nil of which depend upon fruit charac- 

 ters. The habit of the plant, the > ellow flowers, the rudimentary stipe, the thin pod, 

 partially flattened when little more than an ovary, suggest that the plant may be 

 related to A. scopulonuit. 



