Astragalus regiomontanus 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

82. Astragalus regiomontanus Barneby, Mem. New York Bot. Gard. 13: 168. 1964

Type:— MEXICO, Nuevo León, Sierra Madre near Monterrey , 22 August 1889, C. G. Pringle 2887 (holotype: isotype: MEXU 01169238 !, GH 00059434 digital image!, MEXU 00154981 !) .

Perennial; Stems up to 160 cm long, erect, one or several stems from base, basally solid or hollow (when young), striate, branched distally, minute strigose, the trichomes up to 0.3 mm long, basally glabrate or almost so. Stipules 2–4 mm long, semi-clasping, not connate, deltoid to triangular, some decurrent. Leaves 3.5–12 cm long, leaflets 9–23, 5–18 mm long, oblong to ovate, retuse, bicolored, abaxially clearer and pubescent, adaxially glabrate. Peduncles 2–5.5 cm long; the racemes 2–5.5 cm long, flowers 7–15. Flowers white, deflexed; the calyx 5.5–6.1 × 2.7–2.9 mm, strigose, trichomes white, the tube 3.3–3.8 mm long, campanulate, the teeth 2.6–2.9 mm long, subulate; the banner 9–11 × 4.8–5.8 mm, obovate to rhombic, retuse; the wings 9–10.5 × 1.4–2.3 mm, the claw 3.4–3.8 mm long, the blade 7–7.6 mm long, elliptic to oblanceolate, sub-oblique, incurved; the keel 7.4–8 × 2.2–2.4 mm, the claw 3.4–3.8 mm long, the blade 4.4–4.9 mm long, distally oblique, obovate. Pod 1.9–2.6 × 0.4–0.5 cm, deflexed, stipitate (stipe 1.5–2 mm long), triquetrous, compressed, oblong to elliptic, semi-straight or incurved, lateral faces obtuse, ventrally carinate, dorsally wide and openly sulcate, the valves glabrate, papery, turning somewhat rigid with age, ochre, strongly reticulate, septum incomplete; ovules 10–14; seeds 2.6–2.8 mm long, mitten shaped, brown, smooth.

Distribution:— Endemic to Mexico, inhabiting the mountains of central Nuevo León (Linares, Montemorelos and Santiago) ( Fig. 24 ).

Habitat:— Clay soils; shallow or steep slopes; open vegetation; humid canyons; oak forest; oak-pine forest; 1200–1800 m.

Comments:— Six species in Nuevo Leon possess triquetrous pods, of which A. regiomontanus is easily distinguished by its white petals and stipitate podswhich are not found in the other species.

Specimens examined:—NUEVO LEÓN: 4 April 2003, Ejido la Trinidad, Mpio. Montemorelos, C. Yen, E. Estrada 15433 ( CFNL) ; 2 July 2003, Rancho El Encino , 23 km al SW de Linares, por la carretera rumbo a Iturbide, C. Yen, E. Estrada 15803 ( CFNL) ; 27 July 2003, Rancho El Encino , aprox. 23 km al oeste de Linares, por la carrtera rumbo a Iturbide, C. Yen, E. Estrada 15814 ( CFNL) ; 30 July 2003, Linares , N.L, C. Yen, E. Estrada 15133 ( ANSM, CFNL) ; 25 August 1889, Sierra Madre near Monterrey, C. G. Pringle 2559 ( NY, US) ; 4 April 2003, Rancho el Encino, Mpio. Linares, E. Estrada 15444, C. Yen ( CFNL) ; 1934, Sierra Madre Oriental , near Monterrey, C. H. Muller 492 ( MEXU) .

Figures

FIGURE 24. Map showing the distribution of Astragalus regiomontanus, A. rupertii, A. sabulonuum, A. sagitticarpus, and A. sanctorum in Mexico.