Astragalus crassicarpus var. Paysoni

Closely resembling var. crassicarpus, differing principally in the paler herbage, strigulose with usually shorter hairs up to 0.35-0.65 (0.75) mm. long, the less densely pilosulous or merely strigulose inflorescence, and the prevailing slightly larger, paler flowers; stems (0.5) 1-3.5 dm. long; leaves (2) 4-11 (16) cm. long, with 15—25 obovate-cuneate, oval, oblanceolate, or elliptic, obtuse, acute, or rarely truncate-emarginate leaflets 4-16 mm. long, up to 3-7 mm. wide; peduncles (1-5) 2-6.5 (8) cm. long; racemes (5) 8-20-flowered, the axis (1) 2-7 cm. long in fruit, pedicels (2) 2.8—5.5 mm. long in fruit; calyx 9.6—14 mm. long, the tube 7-9.7 mm. long, (3.8) 4-5 mm. in diameter, the teeth (1.9) 2.3-4 (4.4) mm. long; banner (18.3) 20-24 mm. long, (8.6) 9-12 mm. wide; wings 16.4-20.4 mm. long, the claws 7.2-9.7 mm., the blades 10.4-13.6 mm. long, 2.9-4.7 mm. wide; keel (12.6) 13.9-15.9 mm. long, the claws (6.6) 7.4-9.5 mm., the blades 6.5-7.7 mm. long, 3.2-4.1 mm. wide; anthers 0.6-0.85 (0.9) mm. long; pod as in var. crassicarpus; ovules (40) 47-59, averaging ± 52.—Collections: 49 (vi); representative: J. Macoun 18,468 (ND); Hitchcock & Muhlick 11,757 (CAS, NY, RSA, WS), 11,857 (CAS, NY, WS), 12,067 (CAS, NY, RSA, WS); C. L. Porter 2860 (RM, SMU, TEX, WS, WTU), 4163 (RSA, SMU, TEX); Ewan 14,258 (CAS, RSA); Ripley & Barneby 10,360 (RSA); Rydberg & Vreeland 5992, 5993 (NY).

Prairies, grassy hillsides and open knolls, indifferently on granite, shale, sandstone or limestone, westward often among sagebrush, 3300—8600 feet, widespread and common along the east slope and piedmont of the Rocky Mountains, from southern Alberta to southcentral Colorado, perhaps isolated on Black Mesa at the west tip of the Oklahoma Panhandle, extending feebly west across the Continental Divide to the headwaters of the Flathead River and Clarks Fork in western Montana—Map No. 101.—April to July, the fruit ripe in summer and fall.

Astragalus crassicarpus var. Paysoni (Kelso) Barneby in Amer. Midl. Nat. 55: 497. 1956, based on A. succulentus var. Paysoni (Edwin Blake Payson, 1893-1927) Kelso in Rhodora 39: 151. 1937.—"Wyoming: Carbon County, sagebrush slope, Big Creek, road to Encampment, June 30, 1922, Payson & Payson 2514 ... "—Holotyus, US!

Astragalus prunifer (plum-bearing, the fruit known as ground-plum) Rydb. in Mem. N. Y. Bot. Gard. 1 (Fl. Mont.): 239. 1900.—"Wyoming: Medicine Bow, 1897, Aven Nelson ... "— Holotypus, A. Nelson 3143, collected June 5, 1897, NY!

In the foregoing key the mountain ground-plum, var. Paysoni (= Geoprumnon succulentum sensu Rydb., 1929, p. 461 = A. succulentus sensu C. L. Porter, 1951, p. 36, non Richards.) has been distinguished from its prairie counterpart by characters of a trivial and superficial nature. Both varieties of A. crassicarpus are variable in pubescence and flower-size. The average plant of var. Paysoni is less densely pubescent with shorter hairs, the inflorescence being more often strigulose than pilosulous and, if pilosulous, more shortly so; its flowers are, on the average, a little longer. The pods are identical in outward appearance, but the ovules in var. Paysoni are fewer or tend to be so, the number fluctuating around a mean of 52 rather than 60. There is no doubt that two races exist, but no sharp line can be drawn between them, for many collections from a narrow strip along the east base of the Rocky Mountains are quite intermediate in all critical characters and can only be assigned arbitrarily to either category.