52. Astragalus longissimus (M. E. Jones) Barneby, Mem. New York Bot. Gard. 13(1): 183. 1964 Type:— MEXICO, Chihuahua, by streams of the Sierra Madre, C. G. Pringle 1219 (holotype (based on Astragalus rusbyi var. longissimus): US00831412 digital image!; isotype: NDG26787 digital image!, PH00005547 digital image!, F0058947F digital image!, NY00005838!, NY00005839!; isosyntype: NA0095601 digital image!) Astragalus rusbyi Greene var. longissimus M. E. Jones, Proc. Calif. Acad. Sci. ser. 2, 5: 662. 1895. — Atelophragma longissimum Rydb., Bull. Torrey Bot. Club 55: 162. 1928. Atelophragma townsendii Rydb., Bull. Torrey Bot. Club 55: 163. 1928. Perennial. Stems up to 40 cm long, hard o thin but hard, single o several branched form base, ascendant or erect, pubescent, the trichomes up to 1 mm long, sub-appressed or ascending or almost so. Stipules 1.5–8 mm long, clasping to connate, the lowest ones bidentate, forming a sheath around the stem, the upper ones lanceolate or just attached or connate at base only, sometimes free. Leaves 5–15 cm long; leaflets 23–45, 2–14.4 mm long, linear, elliptic to obovate, obtuse or mucronate, adaxially glabrate or subglabrate in midvein or adjacent to it. Peduncles 5–22 cm long, straight o curved, ascendant; the racemes 5–31 cm long, lax, flowers 13–75 pendulous. Flowers ochroleucous, turning opaqueyellow when drying, yellow and white, yellowish; clear yellow, the keel paler; the calyx 3.2–5 × 2.1–3.2 mm, strigose, trichomes black o black and white mixed, the tube 2.4–3.5 mm long; the teeth 0.8–1.6 mm long, subulate or triangular, sometimes one pair shorter and wider; the banner 5.2–8.3 mm × 3.2–5.6 mm, ovate, basally cuneate, recurved, slightly retuse apically; the wings 5.4–8.5 mm × 1.5–2.6 mm, the claw 2–3.5 mm long, the blade 3.7–5.5 mm long, oblong or obovate, incurved; the keel 4.4–6.6 x 1.7–2.5 mm, the claw 2.1–2.8 mm long, the blade 2.8–4 mm long, obovate. Pod deflexed, 13–23.2 × 4–5.2 mm, stipitate (stipe 3–5.5 mm long) oblong, elliptic, to lancoelate, straight o slightly curved, narrowed at both ends, triquetrous, obcompressed, ventrally carinate, dorsally open and slightly sulcate, laterally lightly convex, the angles obtuse, the valves somewhat fleshy, greenish, ochre or bronze with age, rigid papery, softly reticulate, septum partial or complete, the pod thence bilocular or subbilocular; seeds 2–2.5 mm long, mitten shaped, purple or brown. Distribution:— Endemic to Mexico; retricted to the mountains in northwestern Mexico, Sonora and Chihuahua (Fig. 15). Habitat:— Volcanic, gray, rhyolitic soils; pronounced slopes; rocky slopes; cultivated areas; open oak forests; pine-oak forest; coniferous forest with Pseudotsuga; disturbed grasslands; 2225–2400 m. Comments:— The mountains, hills and high plains of northeastern and southwestern Chihuahua adjacent to Sonora harbor at least 15 different Astragalus species, but only four of them have yellow, pale-yellow, lemon-yellow to green-white (A. daleae, A. giganteus, A. hartmanii and A. longissimus). Only A. daleae and A. longissimus have triquetrous pods, but A. daleae has cimbiform (boat-shaped) stipules and relatively short, 7–12 mm long and sessile pod. Specimens examined:— CHIHUAHUA: VIII-1899, Between Colonia Garcia and Pratt’s Ranch below Pacheco, E. W. Nelson 6283 (NY); 17 August 1959, Along railroad tracks between Cuatrocientos and Las Barras de Babicora, A. R. Kruckeberg 4941 (NY); 2 August 1988, 4 mi. E of Ocampo, R. Spellenberg 9651 (NY); 21 October 1968, Between Sta. Ana Babicora and Bachiniva near Sta. Ana Babicora, about 2 mi. w of the summit, R. Spellenberg 2003, M. Spellenberg (NY); 21 October 1968, Between Sta. Ana Babicora and Bachiniva near Sta. Ana Babicora, about 1 mi. w of the summit, R. W. Spellenberg 2005 (NY); 2 August 1988, On Chih. Hwy. 28 at the top of the Cuesta del Toro, 22 km N of Soto Maynez, 16 km S of the junction with the highway to San Jose de Bavicora, 27 km S of Gomez Farias, R. Spellenberg 9666, R. Corral, J. Brunt, L. Huenneke (CIIDIR, IBUG, JEPS, MEXU, NY, US); 26 August 1994, Laguna de Babícora, 15 km al SO de San José de Babícora, C. Yen, E. Estrada 3433 (NY); 27 August 2007, 6 km W of Divisadero at km marker 50 (W of Creel), between San Rafael and Divisadero, R. Spellenberg 13840 (NY); 27 July 1899, Sierra Madre, 10 mi. S. W. of Chuichupa, C. H. T. Townsend 95, C. M. Barber (NY); 10 July 1997, 4 mi NW of Pacheco / Willy jct. on rd. to Rancho Willy, J. Spencer 560, D. Atwood (NY); 26 September 1903, San Diego Canyon, M. E. Jones s.n. (NY); 9 September 1995, Mesa El Campanero, along Hwy 16, 7.8 mi west of Yécora, 1.1 east of Puerto de la Cruz, M. Fishbein 2582 et al. (NY); 1 August 1899 / 20 August 1899, Near Colonia Garcia in the Sierra Madre, E. W. Nelson 6174 (NY, US). SONORA: 16 August 1998, Ca. 6 air km WSW of Yecora, and 2 rd km S of Puerto de La Cruz and Mex. Hwy. 16 on road up to Mesa del Campanero, R. Spellenberg 12638, L. Brouillet, T. K. Todsen (NY); 16/ 17 September 1934, Barranca Colorad, F. W. Pennell 18935 (US); 2 August 2011, ca. 5 road miles W then Nof Rincon de Guadalupe, Sierra de Bacadehuachi, G. Yatzkievych 11-45 (USON); 6 September 1996, 5.2 km west of Yecora on Mex. 16, T. R. Van Devender 96-414, A. L. Reina, A. Burquez M., J. T. Columbus, G. Ferguson, J. F. Wines (MEXU, TEX-LL, USON); 6 October 1985, Bocoyna, R. Bye, E. Linares 14196 (MEXU); 27 July 1974, Between San Rafael and Creel, R. A. Bye 6616 (MEXU).

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