Silver Leaf Milk Vetch

Xylophacos argophyllus (Nutt.) Rydb. Bull. Torrey Club
40:49. 1913.
Astragalus argophyllus Nutt.; T. & G. Fl. N. Am. 1: 331. 1838. Astragalus uintensis M. E. Jones, Proc Calif. Acad. II. 5: 670. 1895. Xylophacos uintensis Rydb. Bull. Torrey Club 32: 662. 1906. Astragalus argophyllus Martini M. E. Jones, Rev. Astrag. 207. 1923. Astragalus argophyllus cnicensis M. E. Jones, Rev. Astrag. 208. 1923.
A perennial, with a cespitose caudex; stems usually less than 1 dm. high, decumbent at the base, hirsute-strigose; leaves 5-10 cm. long, ascending; lower stipules deltoid and short, the upper narrowly lanceolate, 5-15 mm. long; leaflets 13-21, lanceolate, acute, 8-15 mm. long, 2-4 mm. wide, long-strigose on both sides; peduncles 4—8 cm. long, shorter than the leaves; bracts linear-lanceolate, about 5 mm. long; raceme 3-S-flowered; calyx white-strigose, the tube about 1 cm. long, the teeth subulate, 4-5 mm. long; corolla 2-2.5 mm. long, pink-purple; banner oblong-obovate, deeply notched ; wings shorter, the blade oblong, shorter than the claw, with a broad basal auricle; keel-petals much shorter, the blade broadly lunate, obtuse; pod ovoid, hirsute with ascending hairs, 2-2.5 cm. long, 8 mm. wide and thick, short-acuminate, slightly falcate.
Type locality: Valleys of the Rocky Mountains, near the sources of the Platte, Wyoming.
Distribution: Montana and Idaho to Nevada, Utah, and Wyoming.

Perennial, Herbs, Stems woody below, or from woody crown or caudex, Taproot present, Nodules present, Stems erect or ascending, Stems less than 1 m tall, Stems solid, Stems or young twigs sparsely to densely hairy, Stem hairs hispid to villous, Leaves alternate, Leaves petiolate, Stipules conspicuous, Stipules membranous or chartaceous, Stipules persistent, Stipules free, Leaves compound, Leaves odd pinnate, Leaf or leaflet margins entire, Leaflets opposite, Leaflets 10- many, Leaves hairy on one or both surfaces, Flowers in axillary clusters or few-floweredracemes, 2-6 flowers, Inflorescence umbel-like or subumbellate, Inflorescence axillary, Bracts very small, absent or caducous, Flowers zygomorphic, Calyx 5-lobed, Calyx glabrous, Petals separate, Corolla papilionaceous, Petals clawed, Petals pinkish to rose, Petals blue, lavander to purple, or violet, Banner petal narrow or oblanceolate, Wing petals narrow, oblanceolate to oblong, Wing tips obtuse or rounded, Keel petals auriculate, spurred, or gibbous, Keel tips obtuse or rounded, not beaked, Stamens 9-10, Stamens diadelphous, 9 united, 1 free, Filaments glabrous, Style terete, Style persistent in fruit, Fruit a legume, Fruit unilocular, Fruit tardily or weakly dehiscent, Fruit oblong or ellipsoidal, Fruit strongly curved, falcate, bent, or lunate, Fruit rugose wrinkled or reticulate, Fruit fleshy, Fruit coriaceous or becoming woody, Fruit exserted from calyx, Fruit beaked, Fruit hairy, Fruit 11-many seeded, Seeds cordiform, mit-shaped, notched at one end, Seed surface smooth, Seeds olive, brown, or black.