Astragalus camptopus Barneby

Authors

Rupert C. Barneby

Authority

Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(1): 1-596.

Family

Fabaceae

Scientific Name

Astragalus camptopus Barneby

Type

"Idaho: ... 5 miles southwest of Bruneau, Owyhee Co., alt. 2500 ft., 2 June, 1945, fl. & fr., Ripley & Barneby No. 6525 ..."—Holotypus, CAS! isotypi, GH, ID, K, NY, PH, POM, RSA, UTC!

Description

Species Description - Colonial perennial, from an initial taproot with subterranean crown giving rise to slender rhizomes, from which in turn stems originate singly or few together at irregular intervals, the herbage loosely strigulose or villosulous with incumbent or curly hairs, commonly canescent throughout, or the leaflets sometimes more thinly pubescent and greenish above; stems erect or ascending, 2-3 dm. long, leafless and buried for 2-10 cm., becoming stouter and leafy on emergence, simple or few-branched near the middle, the short upper internodes abruptly flexuous or zigzag; stipules 1-3 mm. long, the lowest adnate to a suppressed petiole to form a loose, scarious, semiamplexicaul, bidentate sheath, the median and upper ones deltoid or ovate, herbaceous, cauline; leaves spreading, 3-8 cm. long, with (9) 13-21 obovate-cuneate, obtuse or commonly retuse, sometimes obcordate, flat or loosely folded leaflets 4-12 mm. long; peduncles erect or divaricately ascending, 1-6.5 cm. long; racemes rather loosely 9-15-flowered, the flowers ascending or subhorizontal at full anthesis, the axis becoming 3-8 cm. long in fruit; bracts ovate, acute, ± 1 mm. long; pedicels ascending, at anthesis 1-1.5 mm., in fruit a trifle thickened, ± 2 mm. long; bracetoles 0; calyx 5-6.5 mm. long, thinly villosulous with pale or dark hairs, the oblique disc nearly 1 mm. deep, the campanulate, membranous, often purplish, somewhat inflated tube 5-6 mm. long, 3.6-4 mm. in diameter, the deltoid teeth 0.5-0.9 mm. long, the ventral pair broadest, the whole becoming papery, marcescent unruptured; petals bright pink-purple; banner ovate-cuneate, 14-17 mm. long, 8.5-10 mm. wide; wings 14-16.5 mm. long, the claws 7-8 mm., the broadly lanceolate, slightly incurved blades 7-8 mm. long, 2.8-3 mm. wide; keel 12—13 mm. long, the claws 7—7.5 mm., the half-obovate blades 5—6 mm. long, ± 3 mm. wide, incurved through nearly 90° to the blunt apex; anthers 0.6—0.65 mm. long; pod stipitate, the stipe 1—1.5 cm. long, spreading subhorizontally at base and thereafter arched downward or somewhat contorted distally, gradually expanded at apex into the narrowly oblong body, this 3.5—4 mm. wide, coiled through 1½-2 spirals into a closed ring, strongly compressed laterally, bicarinate by the slender but salient sutures, the dorsal suture often undulate, the scarcely fleshy, pale green, sometimes mottled valves becoming stiffly papery, stramineous, cross-reticulate, thinly villous with spreading or incurved hairs up to 0.7—1 mm. long, not inflexed; seeds (seldom seen) brown, ± 2 mm. long.

Distribution and Ecology - Barren knolls, gulches in the foothills, sagebrush scablands, dunes and dunelike hillsides, in loose sandy soils of basaltic or rhyolitic origin, 2300-3300 feet, locally plentiful and forming colonies, known only from the lower Bruneau Valley and from creeks flowing north into the Snake River below its confluence with the Bruneau in Owyhee County, Idaho.—Map No. 28.—May and June.

Discussion

The Bruneau milk-vetch, A. camptopus, is an ornamental astragalus which in good years clothes the barren, sandy hillsides and low, rhyolitic knolls of the Bruneau Desert with wide patches of ashen foliage, beset in May and early June with abundant pink-purple blossoms. The rhizomatous growth-habit and commonly broad, retuse leaflets are reminiscent of A. (Uliginosi) oreganus, although the flowers and fruits are very different in detail. The pods, when first formed, are pale green, often mottled with reddish-purple, and are borne on slender, decurving stipes which are often sigmoidally or more elaborately contorted. The body of the fruit is nearly always coiled into a complete circle or through two spirals flattened against each other in the manner of a split ring, but an occasional exceptionally short pod may be no more than hamately incurved.

The species was discovered in 1930 by Marcus Jones, who referred it tentatively both to A. speirocarpus and to A. sinuatus, under which name his excellent material (No. 25,420, cited above) was widely distributed, (cf. Jones, Contrib. West. Bot. 17: 16, 29. 1930). The established range of the Bruneau milk-vetch scarcely exceeds fifty miles east and west, but in its area it is common and locally abundant.

Objects

Specimen - 797138, B. Maguire 26220, Astragalus camptopus Barneby, Fabaceae (152.0), Magnoliophyta; North America, United States of America, Idaho, Owyhee Co.

Specimen - 797139, B. Maguire 26351, Astragalus camptopus Barneby, Fabaceae (152.0), Magnoliophyta; North America, United States of America, Idaho, Owyhee Co.

Distribution

Idaho United States of America North America|