Astragalus amphioxys A. Gray var. amphioxys

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

3. Astragalus amphioxys A. Gray var. amphioxys

Type: — USA Not seen; lectotype (Designated by Rydberg 1925): — USA, Doña Ana, New Mexico, Thurber 295, GH 02064315 digital image!

Astragalus amphioxys A. Gray, Proc. Amer. Acad. 13: 366. 1878.

Astragalus crescenticarpus E. Sheld. , Minnesota Bot. Stud. 1: 148. 1894.

Xylophacos amphioxys (A. Gray) Rydb., Bull. Torrey Bot. Club 32: 662. 1905.

Xylophacos aragalloides Rydb, Bull. Torrey Bot. Club 34: 48. 1907.

Annual, or perennial for short time. Stems very short, up to 7 cm long, rarely 10–12 cm long, prostrate o barely ascending, strigose, the trichomes up to 1.5 mm long, dolabriform (joined at one point, before the base, forming a “t” with two arms of different or rarely equal size), sometimes mixed with shorter, straight, rigid, simple appressed trichomes. Stipules 1.5–13 mm long, semi-clasping or the lowest completely clasping, not connate, ovate to triangularovate. Leaves 2–13 cm long, leaflets 7–21, 0.3–2 cm long, elliptic, obovate to lanceloate-obovate, rarely retuse, pubescent. Peduncles up to 20 cm long, curved or humistrate as matures with age, glabrate or with scattered black trichomes; racemes up to 6.5 cm long, with same pubescence as peduncles, flowers 2–13. Flowers rose, rose-purple or white (immaculate), the calyx 9.3–14 × 3.2–4.7 mm, strigose, trichomes white, black or both mixed, the tube 5.6–10.5 mm long, cylindrical to campanulate-cylindrical, the teeth 1.5–4.7 mm long, subulate; the banner 16–24.5 × 8.2–12.2 mm, recurved, spathulate; the wings 15–22.4 × 2.4–4.2 mm, the claw 7–11.5 mm long, the blade 8.3–11.5 mm long, linear-lanceolate, incurved, apically obtuse; the keel 13.2–19.6 × 2.9–3.8 mm, obliquely obovate, the claw 6.5–11.9 mm long, the blade 6.8–9.8 mm long. Pod 1.5–5 × 0.5–1 cm, ascendant, but humistrate, straight or curved, laterally compressed, narrow in both ends, bisutured lenghtwise, the valves fleshy to leathery or almost lignified, reticulated or wrinkled, not inflexed; ovules 42–70; seeds 2–3 mm long, brown, dull or lustrous.

Distribution:— In Mexico, recorded only in the northern end of the state of Chihuahua (Municipio de Juárez), adjacent to the Texas border. Also, in Nevada, New Mexico, Utah and Arizona ( USA) (v. 2).

Habitat:— Planis on sandy soils.

Comments:— Species easily discernible by its dolabriform pubescence.

Specimens examined:—CHIHUAHUA: 4 May 1885, Río Grande, Paso del Norte, C. G. Pringle 201 (NY, US); 25 April 1893, Paso del Norte (today Cd. Juárez), C.G. Pringle s.n (MEXU).