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).