Monographs Details: Astragalus minthorniae (Rydb.) Jeps.
Authors:Rupert C. Barneby
Authority: Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(1): 1-596.
Description:Species Description - Caulescent perennials with erect or stiffly ascending stems, variably pubescent with appressed or widely spreading hairs, the herbage green or canescent, the leaflets commonly bicolored, brighter green and occasionally glabrescent above, the inflorescence black- or partly black-pilosulous; stems few or several, simple, (0.3) 1-3 dm. long, composed of short lower internodes often concealed by stipules and (2) 3-5 developed ones (1) 3-7 (10) cm. long, stipules somewhat dimorphic, the lowest papery-membranous, ovate and mostly obtuse, 4-15 mm. long, adnate to a suppressed petiole and ± strongly amplexicaul-decurrent but free, the pairs together forming a loose sheath often broader than the stem the upper ones progressively narrower, the uppermost subherbaceous, deltoid to lanceolate, mostly acute; leaves (4) 6-17 cm. long, all petioled, with (7) 9-17 obovate-cuneate, ovate, or suborbicular, obtuse or emarginate, rarely elliptic and acute, flat leaflets 8-20 (26) mm. long; peduncles erect, at least the earliest one stout, 6-16 cm. long; racemes loosely 7-35-flowered oblong in early anthesis, the axis elongating, 2.5-12 (25) cm. long in fruit; bracts lanceolate 2-6 mm. long; pedicels at anthesis about 1 mm. long, in fruit thickened, persistent, 2-3.5 m long; bracteoles 0-2, calyx densely pilosulous with mostly black hairs the disc 0.4-0.8 (1.2) mm. in the deeply campanulate or cylindric tube 4.5-5.2 mm. long, 2-2.8 (3.2) mm. in diameter, the subulate teeth 1.5-2.7 mm. long, the ventral pair often broadest and sometimes shortest; petals ochroleucous tinged with dull purple, or luridly vinous-purple with pallid or white wing-tips; banner recurved through ± 45°, 12-17 mm. long, the long-cuneate claw expanded into a rhombic-ovate blade (5) 6.5-9 mm. wide; wings 11-15 mm. long, the claws 4.8-6 mm., the narrowly oblong, nearly straight, obtuse or erose-emarginate blades (6.3) 7-9.8 mm. long, 1.8-2.7 mm. wide; keel 9.5-13 mm. long, the claws 4.8-7 mm., the half-obovate blades 4.5-7.5 mm. long, 2.5-3.2 mm. wide, incurved through 70-80° to the rounded apex; anthers (0.55) 0.6-0.7 mm. long; pod erect or ascending at a narrow angle, subsessile or shortly stipitate, the stout necklike stipe 0.5-1.5 mm. long, the body narrowly oblong-elliptic to linear-oblong or narrowly oblanceolate in profile, straight or gently incurved, 1.5-3 cm. long, 4-6 mm. in diameter, cuneate or rounded at base, abruptly acute and cuspidate at apex, subterete or a trifle laterally compressed when first formed, becoming decidedly compressed in ripening, but the faces remaining convexly rounded as the ventral suture becomes prominent and cordlike, the somewhat fleshy valves becoming leathery, transversely reticulate beneath the vesture, pilosulous or shaggy-villous, inflexed as a complete septum; dehiscence apical and downward about half-way through the ventral suture, the walls of the septum partially separating in age; ovules 22-34; seeds brown or ochraceous, pitted and angled, 2.3-3.4 mm. long.