Usually very slender, sometimes diminutive, with a subfiliform taproot, pilosulous nearly throughout with loosely ascending, incurved, or rarely subappressed, straight or partly sinuous hairs up to 0.35—0.7 (0.75) mm. long, the herbage green or greenish-cinereous, the leaflets commonly pubescent on both sides, but often more thinly so or medially glabrescent above, the inflorescence nearly always black- hairy; stems solitary and erect, or several from near the base, the outer ones then either decumbent or incurved-ascending, 3—23 (30) cm. long, simple or (when robust) few-branched or -spurred below the middle, often floriferous nearly from the base, becoming wiry and zigzag distally in age; stipules submembranous, pallid or green- or purple-tinged, becoming papery, ovate, deltoid, ovate-acuminate, or lanceolate, (1) 1.5-3 mm. long, semi- to almost fully amplexicaul but free; leaves 1-3.5 (4) cm. long, the lowest slender-petioled, the upper ones sessile or nearly so, with 7-13 (15) oblanceolate, linear-oblanceolate, or broadly to narrowly cuneate, sharply retuse, flat or loosely folded, often purple-margined leaflets (1) 2-9 mm. long; peduncles subfiliform, erect, divaricate-, or incurved-ascending, (1) 2-5 (6) cm. long, well surpassing the leaf; racemes 4-15-flowered, dense and headlike in early anthesis, the flowers at first ascending, then spreading and finally declined, the axis soon elongating, 3-20 (27) mm. long in fruit; bracts membranous, pallid, ovate or lanceolate, 0.5-1.3 mm. long; pedicels at early anthesis ascending, 0.2-0.5 mm. long, soon arched outward, ultimately recurved, somewhat thickened, in fruit 0.5-0.9 mm. long, persistent; bracteoles 0; calyx 1.8-2.3 (2.5) mm. long, pilosulous with black (exceptionally white) hairs, the subsymmetric disc 0.2-0.4 mm. deep, the campanulate, turbinate, or (at late anthesis) ovoid-campanulate tube 1.1-1.7 mm. long, 1.1-1.5 mm. in diameter, the subulate or triangular-subulate teeth 0.5-0.9 mm. long, the whole becoming papery-scarious, ruptured, marcescent; petals whitish tinged, veined, or margined with bluish-lilac, sometimes bright violet, the keel marcescent; banner gently recurved through about 25°, oval- elliptic, -obovate, or rarely spatulate, commonly 2.5-3.3 mm. long, 1.5-2 mm. wide, rarely obovate-cuneate and up to 5.5-6.5 mm. long, 3.2-4.2 mm. wide, subentire, shallowly emarginate, or rarely retuse at apex; wings 2.2-2.7 (4.6-5.4) mm. long, the claws 0.8-1.2 (1.7-1.9) mm., the narrowly to broadly oblong (oblong-oblanceolate), obtuse, nearly straight blades 1.5-1.9 (3.3-3.8) mm. long, 0.5-0.8 (1.3-1.5) mm. wide; keel 2-2.5 (3.2-4.2) mm. long, the claws 0.9-1.2 (1.3-2) mm., the blades commonly subquadrangular, 1.1-1.5 mm. long, 0.8-1.1 mm. wide, incurved through 90°, exceptionally half-orbicular, 2-2.4 mm. long, 1.2-1.5 mm. wide, incurved through 100°, the apex bluntly deltoid; anthers 0.15-0.22 (0.25-0.3) mm. long; pod deflexed, sessile, broadly ovate, rhombic-ovate, or nearly circular in dorsal view, 2.8-4.2 mm. long, 2.4-3.6 mm. in diameter, rounded or broadly cuneate and often a trifle retuse at base, abruptly contracted distally into a minute, conic-mucronate beak, strongly obcompressed, very widely and openly sulcate dorsally, the narrow, rugulose-reticulate lateral angles more or less incurved proximally toward the prominent, straight or gently concave-arcuate ventral suture, the thin, green valves hirsutulous (strigulose) with spreading or incurved (more rarely appressed) hairs up to 0.25-0.4 mm. long, becoming papery, stramineous or brownish, inflexed as a complete or subcomplete septum 0.3-0.7 mm. wide; seeds oblong, light or dark brown, sometimes purple-speckled, smooth or nearly so, somewhat lustrous, 1.8-2.3 (2.6) mm. long.—Collections: 111 (xiv); representative: Peck 24,911 (CAS, RSA); C. F. Baker 718 (CAS, ND, NY); Heller 11,273 (CAS, ND, NY); Jones 3229 (NY, POM, WS); Barneby & Howell 11,464 (CAS, RSA); Barneby 11,572 (CAS, RSA).
Open grassy hillsides, valley floors, clearings in chaparral, sometimes in shade of live oaks, in various sandy or clayey soils, sometimes locally abundant on serpentine, 50—2900 (or according to Jepson to 4000) feet, widespread and common throughout the greater part of cismontane California: Sierra foothills from Shasta south to Fresno County; North Coast Ranges inland from the redwood belt, from the lower Trinity River southward; South Coast Ranges, where reaching west to the coast and Channel Islands (Catalina and Santa Cruz); thence south, becoming rarer and somewhat scattered, through cismontane southern California (San Fernando and San Bernardino Valleys to interior San Diego County) to extreme northern Baja California; southern Jackson County, Oregon.—Map No. 159.— March to July.
Astragalus Gambelianus (William Gambel, 1821-1849, physician, ornithologist, friend of Nuttall, one of the first naturalists in California) Sheld. in Minn. Bot. Stud. 1: 21. 1894 ("gambellianus"), an orthographic error, for Sheldon, perhaps following Gray’s annotation of the isotypus at GH, spelled the collector also "Gambell"), based on A. nigrescens (blackening, from the black-hairy racemes) Nutt. in Jour. Acad. Philad. II, 1: 153. 1848 (non A. nigrescens Pall., 1800)—"With the above," i.e., A. catalinensis, "On the island of Catalina, in Upper California."—Holotypus, labeled in Nuttall’s hand: "Astragalus *nigrescens. Catalina.," PH! isotypus, GH (fragm.)!—Hesperastragalus Gambelianus (Sheld.) A. Hell., Muhlenbergia 2: 87. 1905.
Astragalus Elmeri (Elmer Drew, "one of the first to collect it") Greene in Erythea 3: 98. 1895.—"Apparently a local species in Ross Valley, Marin Co., California ... "—Holotypus, collected April 21, 1895, by E. L. Greene, ND (3 sheets)! paratypus, collected in Marin County, April 15, 1891, by Elmer Drew, ND!—Hesperastragalus Elmeri (Greene) Rydb. in Bull. Torr. Club 53: 168. 1926. Astragalus Gambelianus subsp. Elmeri (Greene) Abrams, Il1. Fl. Pac. St. 2: 610. 1944. A. Gambelianus var. Elmeri (Greene) J. T. Howell in Leafl. West. Bot. 5: 107. 1948.
The Gambel milk-vetch, or "Little Bill Loco" (so called by Jepson, with no proof that it is poisonous) is the most widely dispersed and numerically abundant astragalus in California. Because of the small size of the flowers and fruits it is an inconspicuous plant, probably often overlooked; the beauty of the nearly always black-pubescent inflorescence and the uniquely fashioned pod can be appreciated only at the closest quarters. The species varies little. The pod is usually hirsutulous with curly or incurved hairs, but a form, otherwise indistinguishable, with the hairs upwardly appressed and nearly straight was recognized by Rydberg (1926, p. 168) as Hesperastragalus Elmeri (although not the original A. Elmeri of Greene, mentioned further below). I (1950, p. 214) regarded it as a minor variant as did James (1951, p. 71), despite its relatively restricted range along and near the coast from San Francisco south to Los Angeles. The true A. Elmeri Greene is a much more striking variant in which the corolla is almost twice longer than that of normal A. Gambelianus, the banner about 5.5-6.5 mm. long, and other petals in proportion (as noted in parentheses in the description). A very pretty and comparatively showy little plant, A. Elmeri is known chiefly from southern Marin County, particularly from the north slope of Mount Tamalpais (Fairfax Hills; Ross Valley; San Anselmo Canyon), where it has been collected at intervals since 1891 (cf. J. T. Howell 16,942, 21,577, CAS) and is evidently self-productive. I have already called attention (1950, l.c.) to an approximate topotype (Ross Valley, Michener & Bioletti in 1892, NY) consisting of a mixture of small- and large-flowered plants apparently growing together. I have since seen a collection from the Sierra foothills in Amador County (K. Curran, in May, 1886, WS) in which one individual plant among several (including the duplicate at NY) normal examples of A. Gambelianus has a banner 5.5 mm. long. For the present I regard A. Elmeri as a notable variant of uncertain status.