Monographs Details: Astragalus lentiginosus var. oropedii Barneby
Authors:Rupert C. Barneby
Authority: Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(2): 597-1188.
Description:Variety Description - Diffuse perennial, appearing glabrous, the herbage green or subglaucescent, the leaflets beset with a few scattered, subappressed hairs up to 0.4-0.7 mm. long on the lower side, the margins, or the midrib, glabrous above; stems decumbent or weakly ascending, glabrous or nearly so, (1) 2-4 dm. long, flexuous or zigzag in age; leaves 5-14 cm. long, the upper ones subsessile, with 15-21 (25) broadly oblong-elliptic, ovate-oblong, or suborbicular, flat leaflets 5-20 (25) mm. long; peduncles (2) 3-8.5 cm. long, shorter than or subequaling the leaf; racemes shortly (8) 10-25-flowered, the axis little elongating, 1.5-4 (5) cm. long in fruit; calyx 7.5-10.8 mm. long, thinly black- and white-strigulose, the tube (4.5) 5-7.5 mm., the teeth (2.5) 3-5 mm. long; petals purple; banner (12.5) 13.2-20 mm. long; wings 12-18.2 mm., the blades 6.5-10.2 mm. long; keel 11-16.1 mm., the blades 4.8-7.4 mm. long; pod obliquely ovoid or half-ovoid, ± strongly inflated, 1.3-2.5 cm. long, 6.5—14 mm. in diameter, sulcate along both sutures, contracted distally into a triangular-acuminate, laterally compressed, unilocular beak 5-8 mm. long, the valves firmly papery, mottled, glabrous, inflexed as a complete or semicomplete septum 2.8-3.5 mm. wide; ovules 20-33.
Distribution and Ecology - Openings in yellow pine forest, 7000-8000 feet, locally plentiful but apparently confined to the Kaibab Plateau, especially the North Rim and upper levels of the north wall of the Grand Canyon of the Colorado River, Coconino County, Arizona.—Map No. 131.—June to September.
Discussion:The var. oropedii was originally described as combining features of var. Wilsonii, var. palans, and var. diphysus, having the glabrous, subglaucescent herbage and diffuse habit of the first, the individual flower of the second, and the inflated, obliquely ovoid pod of the last. Fruiting specimens are most likely to be compared or confused with var. diphysus but may be distinguished by the long-toothed calyx and the pod of perceptibly thinner texture. The variety is more easily separated from var. vitreus, the freckled milk-vetch prevalent on the north slope of the Kaibab at lower altitudes, by its larger flowers and compact racemes. The only other form of A. lentiginosus known to occur in the Grand Canyon is var. palans, common on the South Rim, and this is easily distinguished from var. oropedii by its uninflated pod of slender outline.
Arizona United States of America North America