Slender, wiry, sparsely leafy, with a woody taproot and knotty root-crown or ultimately a twiggy, suffruticulose caudex, strigulose with rather stiff, straight, filiform or flattened, appressed hairs up to 0.35-0.5 mm. long, the stems often thinly so, the herbage greenish or subcanescent, the leaflets pubescent on both sides, commonly more densely so above than beneath; stems several or numerous, ascending, weak and flexuous when sheltered, stiff and zigzag in open places, (1) 1.5-5 dm. long, simple or usually branched at 1-3 nodes preceding the first peduncle, the branches sometimes again branched, together forming low, tufted clumps; stipules submembranous becoming papery, greenish, pallid, or purple- tinged, ovate or deltoid, (1) 1.5-4 mm. long, semi- or the lowest almost fully amplexicaul; leaves (3) 4-12 (14) cm. long, petiolate but the uppermost quite shortly so or subsessile, with rather stiff rachis and (7) 11-17 (19) rather distant, narrowly to broadly lanceolate or oblong-elliptic, obtuse or retuse, flat or folded leaflets (3) 5-20 (25) mm. long; peduncles erect or incurved-ascending, (1.5) 3-10 cm. long, shorter than the leaf; racemes loosely 10-25-flowered, the flowers ascending at full anthesis, sometimes spreading in age, the axis elongating, (2.5) 4-15 (17) cm. long in fruit; bracts membranous, ovate or ovate-acuminate, 1-1.7 mm. long; pedicels straight or nearly so, ascending, at anthesis slender, 0.4-0.7 mm. long, in fruit thickened, 1—2 mm. long; bracteoles usually 2, minute, sometimes 0; calyx 3.6—6.7 mm. long, strigulose with mixed black and white or almost all black hairs, the asymmetric disc 0.6-1 mm. deep, the submembranous, pallid or purplish tube 2.7—4.1 mm. long, 2.3—3 mm. in diameter, the subulate teeth 0.9-3 mm. long, the whole becoming papery, persistent unruptured; petals little graduated, pale or dark lilac, drying bluish, sometimes whitish lined and distally suffused with pinkish-lilac; banner abruptly recurved through 45-80°, broadly rhombic-ovate-cuneate, sometimes subflabellate, openly notched, 7.1-10.2 mm. long, 5.5—8.1 mm. wide; wings (0.2 mm. shorter, rarely a trifle longer than the banner) 7—9.6 mm. long, the claws 3.1—4.9 mm., the narrowly oblong-oblanceolate, subtruncate or obscurely emarginate, strongly incurved blades 4.2-6.3 mm. long, 1.6—2.7 mm. wide, the inner margins of both infolded; keel (1 mm. shorter to 0.3 mm. longer than the wings) 6.8-9.4 mm. long, the claws 3.1-4.8 mm., the broadly lunate-triangular blades 3.7-5.5 mm. long, 2.3-3.1 mm. wide, abruptly incurved through 95—100° to the sharply triangular, often slightly porrect apex; anthers (0.45) 0.5—0.65 mm. long; pod erect or incurved-ascending at a narrow angle, sessile on a stout gynophore 0.7-1.5 mm. long, the body narrowly oblanceolate in profile, nearly straight or gently incurved (often more so in the lower ? than distally), (2) 2.5—3.1 cm. long, 3.7—5 mm. in diameter, gradually tapering toward the base, abruptly triangular-acute at apex, triquetrously compressed, sharply carinate ventrally by the suture, the lateral angles narrow but obtuse, the lateral faces flat or low-concave and only slightly broader than the shallowly sulcate or ultimately flat dorsal face, the thin, pale green or purple- tinged, glabrous and (when fresh) glaucescent valves becoming papery, stramineous, delicately cross-reticulate, inflexed as a complete septum 2-3 mm. wide; ovules 19-28; seeds not seen.—Collections: 9 (ii); representative: Munz 13,000 (CAS, POM), 13,748 (POM, WS), 17,347 (NY, OKLA, POM); Barneby 11,362 (CAS, NY, POM, RSA).
Gravelly washes and rocky mesas, in granitic or rarely calcareous soils, commonly taking shelter under and entangled in low desert shrubs, 3000-6700 feet, locally plentiful in scattered stations, mountains of southern and eastern Mohave Desert (east base of San Bernardino, Little San Bernardino, New York, and Ivanpah Mountains) in eastern Riverside and San Bernardino Counties, California.—Map No. 145.—April to June.
Astragalus bernardinus (of San Bernardino Mts.) Jones in Proc. Calif. Acad. Sci. II, 5: 661. 1895 ("Bernardinus’’).—"Moronyo King Mine, east side of San Bernardino Mountains, California, 5000° alt., June 16, 1894, Parish."—No holotypus found (1960) at US! phototypus (of plant supposedly at US) + fragments, POM! isotypus, Parish 3001, DS! paratypus, Parish 2581 collected in 1892, labeled by Jones "part of type," GH!—Hamosa bernardina (Jones) Rydb. in Bull. Torr. Club 54: 19. 1927.
The lesser three-keeled milk-vetch, A. bernardinus, is an unassuming, rather weedy astragalus which reveals the beauty of its lilacine or dingily purple flower and smooth, three-sided, glaucescent pod only to the close scrutiny of the curious. In the sagebrush belt of the Great Basin there are several astragali belonging to different groups which are intimately associated with the sagebrush bush itself or with others of similar form and habit, seeming to require their shelter during the seedling stage. During the first season the young plant is concealed and protected by its host, and when mature displays flowers and fruits at the level of its topmost twigs. In the Mohave Desert milk-vetches of this type are few and rare, the others beside A. bernardinus being very local, A. Jaegerianus endemic to mesas north of Barstow and A. atratus var. mensanus to the Death Valley region. Both of these have pendulous pods laterally flattened and persistent on the receptacle, in the former stipitate and carinate by both sutures, in the latter sessile and narrowly grooved along the back.