Astragalus lentiginosus Douglas, Fl.

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

51. Astragalus lentiginosus Douglas, Fl. Bor.- Amer. 1(3): 151. 1831

Phaca lentiginosa (Douglas) Piper, Contr. U. S. Natl. Herb. 11: 368. 1906. — Tragacantha lentiginosa (Douglas) Kuntze, Revis. Gen. Pl. 2: 946. 1891. — Cystium lentiginosum (Douglas) Rydb., Bull. Torrey Bot. Club 40: 50. 1913.

Annual, biennal or perennial. Stems up to 1 m long, single or several from base, prostrate, subrect to erect. Stipules semi-clasping or clasping and decurrent, not connate. Leaves 1–17 cm long, leaflets 11–29, rarely 7. Peduncles 1–10 cm long; the racemes subumbelate or in lax racemes, flowers 3–48. Flowers purple, rose-purple, red-purple, occasionally dark blue when drying; the calyx 3.7–11.9 × 2.5–3.7 mm, the tube 4–7 mm long, cylindrical, campanulate mainly with black trichomes, sometimes densely so, that the tube is black colored, the teeth short, subulate to triangular mainly with black trichomes; the banner 12–14.8 mm long, ovate, basally cuneate, recurved; the wings 11.2–16.6 × 2.5–3.2 mm, the claw 3.9–6.5 mm, the blade 7.4–11 mm, narrow oblanceolate, oblong to linear; the keel 6–16.2 mm long, obovate. Pod 1.2–2.3 cm, sessile, soon caducous, ovoid or globose, inflated, sometimes lanceolate, crescentic or incurved, slightly or not inflated, frequently wide open dorsally, distally curved and ending in a triangular shot or long beak, the valves papery, leathery or papery but slightly stiff-membranous, glabrate or pubescent, septum complete, the pod thence bilocular; ovules 10–23; seeds brown, brown-orange, with purple or purple-black spots, smooth, opaque, rarely lustrous.

Comments:— Several species of Astragalus with with pink, purple, lilac or reddish-lilac or even white with purple, pink or lavender tones flowers and sessile and inflated pods are distributed along the Sonora- Chihuahua border. Some of them have flowers relatively large (banner 7.8 mm long or longer), A. allochrous , A. magdalenae , A. mollissimus and A. sabulonum , and they are morphologically similar and share multiple features in common to A. lentiginosus , but can be differentiated by particular characteristics. Astragalus mollissimus is distinguished from those by its broadened (non-inflated bladder-shaped) and relatively small (9–15 mm long, 4–9 mm wide) pods. Astragalus allochrous and A. magdalenae have smaller flowers (banner 7.8–11 mm long, wider wings, 2–3.6 mm, and the smaller keel, 6.2–9.6 mm long).

Polymorphic species, with 36 varieites ( Barneby, 1964), only two of them are present in northwestern Mexico (Chihuahua and Sonora), and essentially distinguished by the pod shape.

1. Pod 12–22 × 5–15 mm, at least twice as long as wide, slight to strongly inflated, globose to ovoid; northwestern extreme of Chihuahua (Janos) .................................................................................................................................................. A. l. var. australis

- Pod 15–23 × 4.5–6 mm, several times longer than wide, lanceolate or narrowly ovate and acuminate; extreme northeast, northwest and central-northern Sonora ............................................................................................................................... A. l. var. borreganus