Astragalus hypoxylus S. Watson
Creators: name: Castillón, Eduardo Estrada
name: Quintanilla, José Ángel Villarreal
name: Delgado-Salinas, Alfonso
name: Rebman, Jon P.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Fabales
Fabaceae
Astragalus
Astragalus hypoxylus

description: 46. Astragalus hypoxylus S. Watson, Proc. Amer. Acad. 18. 192. 1883   
 Type:— USA, Arizona, Maloney’s Ranch, in the Huachuca Mountains, Southern Arizona, July 1882, J. G, Lemmon 2656 (holotype: GH00058776 digital image!; isotype: UC81373 digital image!).   
 Hamosa hypoxyla (S. Watson) Rydb., Bull. Torrey Bot. Club 54: 336. 1927.   
 Perennial. Stems subterranean and aereal, the aeral up to 23 cm long, single or branched from near base, decumbent, strigose, cinerose, the trichomes up to 0.2 mm long. Stipules 1–1.7 mm long, triangular, not connate. Leaves 1.4–5 cm long, leaflets 9–21, 2–12 mm long, narrow oblong to obovate, obtuse to rounded o acute apically, bicolored, abaxially grayish, adaxially pale green and glabrate. Peduncles 3.5–7 cm long, thin, deflexed to prostrate; the racemes 0.5–2.5 cm long, compact, rounded, ovoid to oblong, flowers 6–18. Flowers white, sometimes the petals with purple tips, lavender, purple or with lilac tones; the calyx 4.8–6.3 × 2–2.1 mm, strigose, the tube 2.6–3.2 mm long, campanulate, sometimes somewhat oblique, the teeth 2–3 mm long, subulate; the banner 7.5–9 mm long, recurved; the wings 6–7.5 × 1.8 mm long, the claw 3–3.2 mm long, the blade 3.5–4 mm long, lanceolate, oblong to obovate; the keel 5.8–6.5 × 1.8 mm long, the claw 3–3.1 mm long, the blade 2.9–3.2 mm long, semi-obovate. Pod 5.6–9 × 2–2.5 mm, ascendant, sessile, triquetrous, dorsoventrally compressed, widened, lanceolate to oblong, straight or slightly incurved, basally obtuse, distally contracted in a short terminal beak, lateral angle-rounded, ventrally carinate, dorsally deeply sulcate, the valves strigose, hard-papery with age, ochre or with reddish-purple tones, imperceptibly reticulate, septum complete, thence the pod bilocular or almost so; ovules 6–8; seeds 1.9–2.3 × 1.2–1.7 mm, brown, mitten shape, smooth, shiny.   
 Distribution:— In Mexico, recorded in mountains of the southeastern Sonora (Yécora), and in the vicinity of Chihuahua, at the height of Bermudez and La Forma. (Fig. 44). Also, in Arizona (USA) (Fig. 13).   
 Habitat:— Rocky streams; hillsides; grasslands in oak and oak-pine forest; 1500–1556 m.   
 Comments:— Rare, on the border of Sonora and Chihuahua. This area harbors another six species of Astragalus (A. daleae, A. gentryi, A. nothoxys, A. nuttallianus, A. pringlei and A. vaccarum) with sessile and triquetrous pods. All of them with stems longer than 23 cm. Sometimes abundant in the areas where it is distributed.   
 Specimens examined:— SONORA: 29 March 1997, Arroyo Agua Caliente (La Soledad), 8 km south of Maycoba on road to Moris (Chihuahua), T. R . Van Devender 97-420, A. L. Reina G. (MEXU, USON); 26 May 2004, Cementery in Yécora, T. R . Van Devender 2004-588, A. L. Reina (MEXU, NY, USON).
description: Published as part of Castillón, Eduardo Estrada, Quintanilla, José Ángel Villarreal, Delgado-Salinas, Alfonso & Rebman, Jon P., 2023, The genus Astragalus (Leguminosae: Papilionoideae: Galegeae) in Mexico, pp. 1921-1935 in Phytotaxa 586 (1) on pages 1921-1935, DOI: 10.11646/phytotaxa.586.1.1, http://zenodo.org/record/7703999