10. Astragalus cenorrhynchus Barneby, Brittonia 34(1): 78–80. 1982

Type:— Mexico, Oaxaca, steep gullied hillsides, near Tepescolula, 6 Novemeber 1964, Ripley 13664 & Barneby (holotype NY!).

Perennial, subterranean stems up to 20 cm long, aereal stems 1–4 cm long, pubescence strigulose, the trichomes appressed, straight up to 0.3–0.4 mm long, the narrow. Stipules of two types, the basal ones, mostly in the subterranean part, semiclasping, 1–1.5 mm long, the upper ones ovate to lanceolate, 1.5–6 mm long, free. Leaves few and small, up to 5 cm long, leaflets 9–15, 3–11 mm long, linear, linear-oblancoelate to linear-elliptic, densely pubescent abaxially, glabrous adaxially. Peduncles only one per plant, sub-basal, 1.5–2.5 cm long, ascending or curved, racemes up to 1 cm long, 7–10 flowered, the flowers soon deflexed, both peduncles and racemes with dense black pubescence. Flowers green-yellow, concolorous; the calyx 4.2–5.8 × 2.2–2.4 mm, the tube 2.6–3 mm, the teeth 1.6–2.8 mm long, subulate; the banner 8–8.5 × 6 mm, obovate, basally cuneate, the wings 5.6–6.2 × 1–1.2 mm, the claw 1.2–1.3 mm, the blade 4.4–5.2 mm long; the keel 6 × 2.3 mm, the claw 2.5 mm long, the balde 3.5 mm long, incurved, apically triangular. Pod sessile, deflexed, 8–10 × 4–5.5 mm, bilocular, trigonous in transversal view, ovoid to semi-ovoid, basally truncate, apically triangular-acuminate, ventrally carinate, lateral faces rounded, dorsally sulcate, the valves coriaceous, stramineous with age, septate, the septum 2 mm wide; ovules 18; seeds 1.2–1.4 mm long, mtten shaped, brown, light brown, sublutrous to opaque.

Distribution:— Endemic to south of Mexico, in Oaxaca (Fig. 3).

Habitat:—S teep gullied hillsides, in red sandy clay soil near 2400 m,

Comments:— A. cenorrhynchus resembles A. hypoleucus Schau., which extends from central Mexico south to the margin of Tehuacan-Cuicatlan Desert along the Oaxaca-Puebla border. Astragalus hypoleucus differs however, in its dolabriform vesture, strongly connate upper stipules, and more slender pod 2.5–4 (not 2) times as long as its diameter (Fig. 9).

Specimens examined:— OAXACA: 6 November 1964, near Teposcolula. H. D. Ripley & R. C. Barneby 13664 (NY); 28 June 2012, Tepsecolula, A. Ibarra 82, J. M. Miguel, A. Cruz, L. Cruz, A. Cruz R. (MEXU).