55.3. Astragalus magdalenae Greene var. peirsonii (Munz & McBurney) Barneby, Aliso 4: 135. 1958

Type:— USA, Arizona, Imperial County, sand dunes between Holtville and Yuma, 15 April 1921, (holotype (based on Astragalus peirsonii): UC495108: isotype MO149247 digital image!, GH58874) .

Astragalus peirsonii Munz & McBurney ex Munz, Bull. S. Calif. Acad. 31: 67. 1932.

Stems up to 1 m tall; leaflets 3–13; terminal leaflet narrow, longer and of different shape than the terminal leaflets pair; reported with petals purple or purplish and the banner with white spot.

Distribution:— In Mexico recorded only in El Pinacate Biosphere Reseve (31°34’24’’N – 113° 30’48.9’’W and 31°37’15’’N, 113°39’10.5’’W), in extreme northwestern Sonora. Also in California (USA) on the Algodones Dunes (Fig. 16).

Habitat:— Sandy dunes; sand hummocks; although of restricted distribution, it is locally common in the areas where registered. Associated with creosote bush; sparse vegetation with starbush; lava fields in the Pinacates; 60– 129 m.

Comments:— Variety easily distinguishable by the number of leaflets, especially the terminal decurrent leaflet, resembling a mere projection of the rachis, longer than the rest of the leaflets, as well as its pod and seed size, both, larger than the other varieties.

Specimens examined:—SONORA: 15 March 2010, dunes 8.5 km NE (36°) of the old train station at Gustavo Sotelo, ca. 35 km NW of Puerto Peñasco, B. T. Wilder 10-64, E. Ezcurra, P. Dayton, G. Dayton, A. Martínez-Greenja, N. Pietrasiak, L. Weller (USON, SD) ; 28 May 2005, Mpio. Puerto Peñasco, Reserva de la Biósfera Alto Golfo, y Delta del Río Colorado,, near shore at 5.8 miles,on dirt road (to La Salina), south of Estación López Collada, R. Felger 05- 318, et al. (SD, USON) ; 16 March 1970, ca. 1 mile south of Moon Crater (Crater Chichi), SW parto f Pinactae Region, R. S. Felger 19010, C de Rosa (ENCB, SD) ; 23 March 1989, Desierto de Altar, E. Ezcurra s.n., R. Medina, Al Flores (MEXU) .