Astragalus acutirostris S. Watson

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

1. Astragalus acutirostris S. Watson , in Proc. Amer. Acad. Arts 20: 360–361. 1885

Type: — USA, “Near Brown’s Ranch, Mohave Desert , S.B. & W. F. Parish 1276, May, 1882 (Holotype GH 00058614 digital image!; isotypus, GH 00058615 digital image!).

Oxytropis acutirostris (S. Watson) M. E. Jones, Proc. Calif.Acad. Sci. II , 5: 677. 1895. — Spiesia acutirostris (S. Watson) M. E. Jones, Proc. Calif. Acad. Sci. ser. 2, 5: 677, in obs. 1895. — Aragallus acutirostris (S. Watson) A. Heller, Cat. N. Amer. PI. 4. 1898. — Hamosa acutirostris (S. Watson) Rydb., Bull. Torrey Bot. Club 54: 331.

Astragalus nuttallianus DC. Var. acutirostris (S. Watson) Jeps., Fl. Calif. 2: 379. 1936.

Annual. Stems up to 30 cm long, erect to decumbent or prostrate, pilose, strigose, trichomes incurved, ascending to appressed up to 0.6 mm long. Stipules semi-clasping, not connate, 0.8–3 mm long, triangular ovate to lanceolate, subglabrate, trichomes black and white mixed. Leaves 1–5 cm long, leaflets 7–15, 2–8.5 mm long, oblong to obovate, truncate or retuse apically, cinerous, bicolored, abaxially brighter. Peduncles 2–7 cm long, straight, rarely bent, surpassing the leaves; racemes 1–4.5 cm long, flowers 1–6. Flowers white with purple or white with lilac tones; calyx 2.6–4 mm long, the wings 4.3–6.2 × 1.1–1.6 mm, claw 1.2–2 mm long, the blade 3.3–4.6 mm long, apically oblique, oblanceolate; the keel 4.2–5.8 × 1.3–1.7 mm, the claw 1.4–2.2 mm long, the blade 3–3.8 mm long, subelliptic, apically ending in a acute beak, incurved. Pod 12–30 x 2–3 mm, stipitate, the stipe 0.3–0.8 mm long, the body straight, ascending or pendulous, linear-elliptic, triquetrous, curved, basally acute, apically abruptly contracted into a short beak or gradually narrowing to the apex, laterally compressed, valves thin, minute strigose or rarely glabrate, green or purple, turning dark brown with age, sublustrous, reticulate; septum complete, thence bilocular, forming two chambers, early caducous from receptacle; ovules 12–26; seeds 1.5–2.5 mm long, olive to dark brown, sometimes with purple tones, dull.

Distribution:— In Mexico, restricted to Baja California in the Sierra Juárez, La Rumorosa, El Rosario, San Quintín, Punta Prieta and Laguna Mormona. Also, in southern California and Nevada ( USA) ( Fig. 2 ).

Habitat:— Metamorphic and saline soils; rocky plains with gravel; deep streams; hillsides; common in coniferoak-juniper forest; associations of pinyon-juniper-oak; 300–1375 m.

Comments:— Species quite similar to some varieties of A. nuttallianus , although the latter has sessile and persistent pods in the receptacle; similar also to A. emoryanus , but the latter has ovary and pod glabrous.

Specimens examined:— BAJA CALIFORNIA: 4 May 1973, east slope of Cerro Matomi , Reid Moran 20795 ( NY, SD); 19 April 1958, 16 km southeast of El Rosario, P. H. Raven 12542 ( CAS, NY) ; 16 May 1982, Sierra Juárez , 4 km SW of la Rumorosa, R. Moran 30739 ( ENCB, SD); 15 May 1977, Sierra Juárez , 5 km west of La Rumorosa, R. Moran 24127 ( CAS, SD); 1 May 1966, Sierra San Borja , on east slope, west peak, Cerro Santa Marta, R. Moran 13113 ( SD); 2 April 1991, 22 mi NE of El Arco on road to San Francisquito S. Boyd 5748, T. Ross ( MEXU) .

Figures

FIGURE 2. Map showing the distribution of Astragalus acutirsotris, A. allochrous, A. amphioxys, A. anemophilus, and A. aridus in Mexico.