Astragalus hidalgensis (Rydb.) Barneby, Mem.

Castillón, Eduardo Estrada, Quintanilla, José Ángel Villarreal, Delgado-Salinas, Alfonso & Rebman, Jon P., 2023, The genus Astragalus (Leguminosae: Papilionoideae: Galegeae) in Mexico, Phytotaxa 586 (1), pp. 1921-1935 : 1921-1935

41. Astragalus hidalgensis (Rydb.) Barneby, Mem. New York Bot. Gard. 13(1): 175. 1964

Atelophragma hidalgense Rydb., Bull. Torrey Bot. Club 55: 159. 1928.

Astragalus strigulosus var. gracilis Hemsl., Biol. Centr. - Amer., Bot. 1: 266. 1880.

Perennial. Stems up to 70 cm long, decumbent or slightly ascending, strigose, the trichomes up to 0.4 mm long. Stipules 0.7–5 mm long, connate at least the lowest ones, bidentate, the upper ones amplexicual. Leaves 1–6 cm long, leaflets 13–23 ovate, 2–12 mm long, oblong to obovate, distally truncate or retuse, occasionally mucronate, bicolored or brighter and glabrate adaxially. Peduncles 3.5–9.5 cm long, thin, erect to incurved; the racemes 1.5–12 cm long, lax, flowers 5–17, soon pendulous. Flowers white, lilac, yellow, bluish or purple with lilac tones, rarely blue; the calyx 3.4–4.5 × 1.9–2.3 mm, strigose, trichomes black or white and black mixed, the tube campanulate, 2.3–2.7 mm long, the teeth subulate, 0.9–1.8 mm long; the banner 6.7–8 × 4–4.8 mm, obovate to oblanceolate, shallowly or evidently retuse; the wings 6.4–6.9 × 1.7 mm, the claw 2–2.6 mm long, the blade 5–5.6 mm long, oblanceolate, truncate o briefly emarginate; the keel 4.8–5.6 × 1.7–1.9 mm, the claw 2.3–2.5 mm long, the blade 3–3.3 mm long, semi-obovate, strongly incurved. Pod 1.2–2.3 x 0.4–0.5 cm, pendulous, stipitate (the stipe 0.5–1.2 mm long) oblong, elliptic to obovate, straight o slightly curved, narrowed at both ends, dorsoventrally compressed or triquetrous, narrow and strongly flattened laterally, ventrally carinate, dorsally shallowly and widely sulcate, the valves hard papery, minute pulverulent when young, glabrate with age, brown, smoothly reticulate, septum complete, the pod two-celled; ovules 9–18; seeds 2.5–2.7 mm long, rounded, mitten shape, brown to light-brown, smooth, somewhat shiny.

Distribution:— Endemic to south of Mexico. Mountains of Hidalgo (La Misión, Pacula, Jacala de Ledezma, Encarnación, El Sabino and north of Zimapán), and areas adjacent to the geopolitical border with Querétaro.

Comments:— From the eight Astragalus species distributed in this region only A. hidalgensis and A. strigulosus has oblong, elliptic to obovate (non inflated bladder-like), tumescent (bulged) and stipitate pods. Both species can be recognized based on the leaf size, leaflets number and petal size. A. strigulosus has longer leaves (4–10 cm long), longer leaflets (in average 18 mm long), more flowers per raceme (12–40) and longer petals (banner 9.2–11.5 mm, wings 7.7–10.5 mm, keel 6.7–7.5 mm).

Two varieties are recognized based on raceme and pod size. Both varieties are sympatric, and, inhabit the same habitat.

1. Peduncles 3–5 cm long, as long as the leaves; racemes 1–3 cm long in fruit; pod 1.3–1.4 × 0.5 cm; pod always flattened; Hidalgo and Querétaro ............................................................................................................................................................. var. hidalgensis

- Peduncles 6–9.5 cm long, much longer than leaves; racemes 5–12 cm long in fruit; pod 1.2–2.3 × 0.4–0.5 cm; pod flattened, rarely triquetrous; Guanajuato, Hidalgo and Querétaro .......................................................................................................... var. protensus