Astragalus pubentissimus

1.5-3 mm. long; pedicels at anthesis 0.5-1.4 mm. long, in fruit arched outward, a little thickened, 1—2 mm. long, persistent; bracteoles 0; calyx 5.4—6.2 mm. long, villosulous (strigulose) with white and rarely a few black hairs (0.3) 0.4-1 mm. long, the oblique disc 0.4-1 mm. deep, the obliquely campanulate, reddish tube 2.8-4.1 mm. long, 2.3-2.9 mm. in diameter, the subulate or subulate- setaceous teeth 1.8—2.8 mm. long; petals pink-purple, the banner striate; banner recurved through 50—90°, ovate-, oval-, or obovate-cuneate, 8.8—11.7 mm. long, 5.5—8 mm. wide; wings 8.7—10.9 mm. long, the claws 3.1—4.3 mm., the lunately oblanceolate or narrowly obovate, obtuse or emarginate blades 5.9—8.1 mm. long, 2-2.8 (3.1) mm. wide; keel 7.3-8.7 mm. long, the claws 3-4.1 mm., the lunately half-obovate blades 4-5 mm. long, 2.2-2.7 mm. wide, incurved through 90-110° to the bluntly triangular or deltoid apex; anthers (0.35) 0.4—0.7 mm. long, pod spreading or declined, sessile, very obliquely lance-ellipsoid, 1.2—2 cm. long, 4—8 mm in diameter, rounded or broadly cuneate at base, contracted distally into a short, deltoid or deltoid-acuminate beak, the body strongly turgid or inflated, carinate ventrally by the filiform but prominent suture, shallowly sul- cate dorsally, incurved through ¼ to slightly over ½-circle, the thin, green or reddish valves becoming papery, stramineous, finely reticulate, thinly shaggy- pilose with lustrous, divergent hairs 1.2-2.2 mm. long, not inflexed; dehiscence apical, after falling: ovules (9) 11—18; seeds olivaceous or dark brown, smooth, dull or sublustrous, 2-2.5 mm. long.—Collections: 21 (viii); representative: M. Ownbey 3247 (NY, WS); Ripley & Barneby 7888 (CAS, RSA, UTC);

Barneby 12,703, 12,721 (CAS, NY, RSA); Jones (from Nine-Mile Canyon) in 1896 (CAS, NY, POM).

Gullied bluffs, stony washes, eroded clay knolls, and benches among junipers, usually in light, alkaline, alluvial soils derived from shales or sandstones, 5100-7000 feet, locally plentiful in the Green River and Uinta Basins, southwestern Wyoming, northeastern Utah, and immediately adjoining northwestern Colorado, and extending south in Utah to the base of Tavaputs Escarpment and the San Rafael Swell in Grand and northern Emery Counties.—Map No. 123.—May to early July.

Astragalus pubentissimus (very hairy) T. & G., Fl. N. Amer. 1: 693. 1840, based on A. multicaulis (many-stemmed) Nutt. ex T. & G., op. cit. 335. 1838 (non A. multicaulis Ledeb., 1831).—"Dry sterile hills near Ham’s Fork of the Colorado of the West... Nuttall." —Holotypus, labeled by Nuttall: "Astragalus * multicaulis. Ham’s Fork of Colorado of the West.," BM! isotypi, GH, NY, PH!—Tragacantha pubentissima (T. & G.) O. Kze., Rev. Gen. 947. 1891. Phaca pubentissima (T. & G.) Rydb. in Bull. Torr. Club 40: 48. 1913.

Astragalus Peabodianus (George Foster Peabody, 1852-1938, banker and philanthropist) Jones in Zoë 3: 295. 1893.—"...at 5,000 feet altitude, Thompson’s Springs, Eastern Utah, May 7, 1891."—Holotypus, POM (2 sheets)!

The Green River milk-vetch, A. pubentissimus, is distinguished among the short-lived Inflati by its comparatively little swollen, lunately incurved pod of papery texture beset with exceptionally long and lustrous hairs. In the Green River and Uinta Basins it is the only astragalus of its type other than the thinly strigulose A. Geyeri (differing further in its tiny, whitish flowers) and is therefore easily recognized even at early anthesis. South of Tavaputs Escarpment, however, the range of A. pubentissimus overlaps or abuts on those of A. sabulonum and A. pardalinus, and without ripe or at least fully formed fruits these three closely related and habitally similar species are difficult to tell apart. The smaller flowers, shorter calyx-tubes, and ordinarily narrower and sharper keel-tips are decisive differential characters both of A. sabulonum and of A. pardalinus, but they require close observation and careful measurement. The high ovule-number (20-28 rather than 10-18) distinguishes A. pardalinus from both its relatives.

The range of A. pubentissimus probably extends farther north than is shown on the distribution map, but I have no precise locality outside the Green River Valley. The species was encountered by the Northwest Wyoming Expedition in 1873 (Parry 76, NY, PH), possibly in the Wind River Valley, and is to be expected in the Big Horn Basin. On the lower White River near Rangely, Colorado, A. pubentissimus has fallen under suspicion as a stock poison (Brown & Jensen in 1958, NY).