Astragalus uncialis Barneby

Authors

Rupert C. Barneby

Authority

Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(2): 597-1188.

Family

Fabaceae

Scientific Name

Astragalus uncialis Barneby

Type

"Nevada: ... in the vicinity of Currant, northeastern Nye Co., alt. 5300 ft., 22 May 1941, Ripley & Barneby No. 3563."—Holotypus, CAS! isotypus, RSA!

Description

Species Description - Dwarf, densely tufted, composed of 1—several sessile crowns arising from a woody taproot or shortly forking caudex beset with a thatch of stipules and leaf- bases, the herbage silvery-strigose with rather coarse, lustrous, straight, appressed and often a few ascending hairs up to (0.85) 1—1.5 mm. long; stipules membranous, pallid with green midrib, 3—6.5 mm. long, almost fully amplexicaul but free, the imbricated blades deltoid-ovate or lanceolate, pubescent dorsally, or the innermost ones subglabrous, all ciliate; leaves 1.5—7.5 cm. long, with slender, wiry petioles and 3—5 sessile but articulate, oblanceolate, elliptic, or narrowly obovate, acute or subobtuse, flat leaflets 5—17 mm. long, the 3 upper ones approximate and subpalmately disposed, the lower pair, when present, rather remote; peduncles scapose, shorter than the leaves, 0.5-3.5 cm. long, ascending at anthesis, prostrate in fruit; racemes subcapitately 1—3-flowered, the flowers suberect, the axis not over 3 mm. long in fruit; bracts membranous, ovate or lance-ovate, 1.5-3.5 mm. long; pedicels ascending, at anthesis 1.5-2.5 mm., in fruit a trifle thickened, 2.5-3 mm. long; bracteoles usually 0, minute when present; calyx 12—16 mm. long, strigulose with white or sometimes also a sprinkling of black hairs, the oblique disc 1.4-2 mm. deep, the cylindric, straight or slightly decurved, pallid or purplish tube 10.2-13 mm. long, 3.8-5.2 mm. in diameter, the lance-subulate teeth 1.8-3.5 mm. long; petals bright pink- or violet-purple, the banner with a pale, striate lozenge in the fold; banner recurved through ± 45°, oblanceolate, notched, 24.5-32 mm. long, 10-12.5 mm. wide; wings as long or a little shorter, 24.5-28.5 mm. long, the claws 12.5-14.8 mm., the narrowly oblong or lance-oblong, obtuse, straight or slightly incurved blades 13-15 mm. long, 2.6-3.3 mm. wide; keel 21.5-24.5 mm. long, the claws 11.5—14 mm., the narrowly obovate-elliptic blades 10—11.5 mm. long, 3.5-4.1 mm. wide, very gently incurved through ± 45° to the broadly rounded apex; anthers 0.7—0.85 mm. long; pod ascending (humistrate), obliquely oblong- or lance-ellipsoid, (2) 2.5-3 cm. long, 8.5-12 mm. in diameter, obtuse or shallowly retuse at base, very strongly obcompressed and nearly straight in the lower %, thereafter abruptly incurved into a broad, deltoid- or triangular-acuminate, laterally compressed beak, ventrally and sometimes also dorsally (but there less strongly) carinate by the salient but depressed sutures, the thinly fleshy valves strigulose with appressed hairs up to 0.6-0.7 mm. long, becoming leathery, brownish-stramineous beneath the silvery vesture, finely cross-reticulate and a little rugulose on the lateral angles, not inflexed; dehiscence apical, through the beak, tardy; ovules 38-54; seeds (immature) orange-brown, apparently smooth, ± 2 mm. long.

Distribution and Ecology - Dry knolls and gullies, in sandy or gravelly, alkaline soils derived from comminuted limestones, 5300-6050 feet, rare and local, known only from the foothills of the White Pine and Pancake Ranges, northeastern Nye County, Nevada.—Map No. 79.—May and June.

Discussion

The Currant milk-vetch, A. uncialis, is one of the most strongly characterized and one of the most ornamental dwarf astragali discovered in recent years. It should be easily recognized by its silvery 3-5-foliolate leaves gathered into radical tufts and by its narrow, long, and showy purple flowers which seem quite disproportionately large for the plant’s diminutive stature. The species is apparently related, although not very closely, to A. musiniensis, from which it differs in its smaller, ordinarily narrower leaflets and in its appressed-pubescent pod of much thinner texture and narrower outline. The species seems to be truly rare as well as local, for careful search in favorable years has turned up only a few plants in each of the two known stations. It will no doubt be found elsewhere on the limestones of eastcentral Nevada, a sector of the Great Basin of which the botanical riches are poorly known.

Distribution

Nevada United States of America North America|