73. Astragalus pomphocalyx Villarreal & M. A. Carranza, Brittonia 46(4): 337. 1994

Type:— MEXICO, Coahuila, Mpio. Ramos Arizpe, Hwy 40, 30 miles W of Monterrey, 21 March 1964, T. Bruny & R. Pena 31 (holotype: TEX00371250!) .

Perennial. Stems up to 40 cm long, erect or ascending, densely villous, whitish, trichomes up to 0.9 mm long. Stipules 3–6 mm long, free, triangular to ovate, the lowest ones auriculate, not connate. Leaves 8–10 cm long, leaflets 15–19, 9–12 mm long, elliptic to ovate, retuse, densely villous, the trichomes adpressed, abaxially denser. Peduncles 3–5 cm long, straight or curved; the racemes 2–5 cm long, dense, subcapitate, flowers 10–30. Flowers blue; the calyx 9–10 × 3–5 mm, urceolate to globose, densely villous, trichomes white only, the tube 4–5 mm long, the teeth 4–5 mm long, subulate; the banner 16 × 8 mm, elliptic, retuse; the wings 13 × 3 mm, the claw 5 mm long, the blade 5 mm long, oblique, oblong to oblanceolate, slightly incurved; the keel 11 × 3.2 mm, the claw 5 mm long, the blade 6 mm long, somewhat obovate. Pod 6–8 × 4–6 mm, sessile, sub-oblong, widened, stiff, inflated but no bladder-like, laterally somewhat compressed, basally rounded, distally contracted abruptly in a triangular conic beak, with the persistent style for a time, ventrally sulcate along straight suture, dorsally widely and openly sulcate, the valves rigid, scattered strigose; septum complete, the pod two-celled; ovules 4; seeds mitten shape, smooth.

Distribution:— Endemic to Mexico, northeast Mexico, semi-arid regions in the geopolitical zone southwest of Coahuila (Estación Vega, 25°26’N, 101°06’W) and central-east (Mina, 25°40’2”N, 100°45’06 “W) of Nuevo León (Fig. 22).

Habitat:— Stony soils; maguey scrubland, acacia scrublands; 1800 m.

Comments:— In the distribution area of A. pomphocalyx, seven other Astragalus species are distributed, but, only three of them ( A. mollissimus, A. pomphocalyx and A. rupertii) have simple pubescence, blue, purple or violet flowers (never red or yellow) and inflated (but no of papery consistence) and widened pods; A. mollissimus is distinguished from the other two ones by its larger petals (banner 15.3–25 mm, wings 14.5–20 mm, the keel 11–13.6 mm). Astragalus pomphocalyx and A. rupertii has several features that distinguish them from each other, however, the latter has longer peduncles, regularly surpassing leaves (rarely as long as these), its racemes are more lax (up to 10 cm long, non-compact), and the oblong-urceolate calyx (non-globose-urecolate) and densely strigose, with black trichomes (sometimes some white trichomes present).

Specimens examined:— COAHUILA: 5 June 1992, Estación de Microondas Vega, 8 km. W de Saltillo, Carretera 40, J. A. Villarreal 6644, M. A. Carranza, D. E. Lozano, S. Comparán (ANSM, MEXU, NY) . NUEVO LEÓN: 21 March 1964, Highway 40, 31 mi W of Monterrey, A. Bruni 31, R. Pena (NY) .