62.5. Astragalus nuttallianus DC. var. trichocarpus Torr. & A. Gray, Fl. N. Amer. 1: 333. 1838

Type:— USA, Texas, 1833, T. Drummond s.n. (holotype: NY00005570!; isotype: US00004252 digital image!, BM001042704 digital image!) .

Astragalus trichocarpus Scheele, Flora 26 (No. 27): 442. 1843.

Leaflets elliptic to ovate, obtuse to acute, rarely some leaflets retuse; calyx teeth 1.5–3 mm long, the trichomes hispid to ciliate, up to 1.2 mm long; pod hirsute, the trichomes up to 1mm long.

Distribution:— Exclusive of north of Mexico, at several isolated localities; central Chihuahua (surrounding Chihuahua City, 28°39’N – 106°05’W), northwest Durango (Tepehuanes and Luis Moya, 25°20’N – 105°43’W) and southwest Coahuila (Estación Carneros, 25°07’N –10106’W). Also, in Texas (USA) (Fig. 19).

Habitat:— Clayey, sandy, gravelly and stony soils; desert scrub; acacia scrubland; grasslands; 200–1981 m.

Comments:— Sometimes forming dense colonies, giving the landscape a bluish color.

Specimens examined:—CHIHUAHUA: 4 April 1885, Hills and plains near Chihuahua, C. G. Pringle 276 (NY, MEXU, US) ; 13 April 1891, Puente de St. Diego, C. V. Hartman 595 (NY) ; 14 April 1886, Plains near Chihuahua, C. G. Pringle 853 (NY) ; 1–21 May 1908, Vicinity of Chihuahua, E. Palmer 171 (NY) . COAHUILA: 23 October 1963, Carneros Pass, 23 miles s. of Saltillo, H. D. Ripley, R. C. Barneby 13268 (NY) ; DURANGO: 10 November 1963, Luis Moya, H. D. Ripley, R. C. Barneby 13508 (NY); 4–25 June 1906, Tepehuanes, E. Palmer 259 (NY); 4 June 1906, Collected at Tepehuanes, E. Palmer 259 (NY) .