860 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
Plants decumbent to prostrate; pods 3 mm. in diameter, 
oblong, about 1 em. long........- 35. A. fleruosus. 
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 em. high............--------2------- 39. A. thurberi. 
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. wootont. 
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.............-.------2-0-- 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. greenet. 
Pods sessile, sublunate (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 em. long................- 48. A. neomericanus. 
Leaflets oblong to obovate, obtuse, few; peduncles shorter, 
less than 20 cm. long. 
Flowers small, 10 mm. long or Jess; pods of about the 
same length; stems usually short....49. A. tephrodes. 
Flowers larger, 12 to 15 mm. long; pods 15 to 20 mm. long; 
stems 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, all of which depend upon fruit charac- 
ters. The habit of the plant, the yellow flowers, the rudimentary stipe, the thin pod, 
partially flattened when little more than an ovary, suggest that the plant may be 
related to A. scopulorum. 
