Crescent Milkvetch

Xylophacos aragalloides Rydb. Bull. Torrey Club 34: 48. 1907
Astragalus cyaneus S. Wats. Am. Nat. 9: 270, in part. 1875. Astragalus amphioxys A. Gray, Proc. Am. Acad. 13: 366, in part. 1878.
A perennial, with a cespitose caudex; stem about 1 dm. long, densely white-strigose; leaves 10-15 cm. long; stipules scarious, strigose, deltoid, 5-8 mm. long; leaflets 11-19, lanceolate or lance-elliptic, silky-canescent, 5-12 mm. long, 2-4 mm. wide; peduncles 5-10 cm. long; racemes 4-10-flowered; bracts lanceolate, 5-7 mm. long, attenuate; calyx strigose with black and white hairs, the tube 8 mm. long, the teeth subulate, 3-4 mm. long; corolla purplish, about 2 cm. long, similar to that of the preceding; pod lunate, tapering at each end, about, 4 cm. long, 7-8 mm. wide, deeply sulcate below, cross-reticulate, sparingly silky-strigose, curved about one third of a circle.
Type locality: St. George, Utah.
Distribution: Southwestern Utah and northern Arizona.

Xylophacos amphioxys (A. Gray) Rydb. Bull. Torrey Club 32:662. 1906.
Astragalus succumbens A. Gray, in J. C. Ives, Rep. Colorado Riv. Bot. 10. 1860. Not A. succumbens Dougl. 1831.
Astragalus Shortianus minor A. Gray, Proc. Am. Acad. 6: 211, in part. 1864.
Astragalus cyaneus S. Wats. Am. Nat. 9: 270. 1875. Not A. cyaneus A. Gray. 1849.
Astragalus Shortianus S. Wats.; Wats. & Rothr. Cat. PI. Wheeler's Surv. 7. 1874. Not A. Shortianus Nutt. 1838.
Astragalus amphioxys A. Gray, Proe. Am. Acad. 13: 366. 1878.
Astragalus crescenticarpus Sheldon. Minn. Bot. Stud. 1: 148. 1894.
Astragalus selenaeus Greene, Erythea 3: 76. 1895.
A perennial or biennial, with a deep root; stems several from the base, about 1 dm. high, silvery-canescent ; leaves ascending, 5-10 cm. long; stipules deltoid, scarious, 3-5 mm. long, canescent; leaflets 1 1—17, obovate, silky-canescent with hairs tapering at each end, 6—12 mm. long, 4-6 mm. wide, mostly obtuse at the apex; peduncles 5-10 cm. long; racemes 4—12flowered, 2-6 cm. long; bracts lanceolate, 2-4 mm. long; calyx silky-canescent, the tube 8 mm. long, the teeth subulate, 3 mm. long; corolla purple, moderately arched at the middle, with a pale spot; blades of the wings oblanceolate, slightly lunate, obtuse, about as long as the claws; keel-petals broadly lunate, rounded at the apex; pod narrowly lunate, tapering at each end, arched nearly into a semicircle, 3-4 cm. long, 6-7 mm. wide, and 4—5 mm. thick, somewhat sulcate on the lower suture, cross-reticulate, silky-strigose.
Type locality: Dona Ana, New Mexico.
Distribution: Texas to southern Utah, Arizona, and northern Chihuahua.

Xylophacos melanocalyx Rydb. Bull. Torrey Club 52: 149. 1925.
Astragalus amphioxys M. E. Jones, Rev. Astrag. 214, in part. 1923. Astragalus amphioxys X Layneae M. E. Jones, Rev. Astrag. 215. 1923.
A perennial, with a cespitose calyx; stems many, 2-7 cm. long, decumbent or ascending, white-strigose, densely covered with leaves; leaves 5-10 cm. long, ascending or spreading; stipules deltoid, 5-8 mm. long, white-strigose; leaflets 11-19, oval or obovate, 5-10 mm. long, 2-5 mm. wide, white silky-strigose on both sides, obtuse at each end; peduncles 7-15 cm. long, erect, white-strigose; bracts lanceolate, 2-3 mm. long, membranous; flowers subsessile; calyx black-hairy, the tube 6-7 mm. long, 3-3.5 mm. broad, the lobes deltoid-subulate, 2 mm. long; corolla bluish-purple, 15-18 mm. long; banner obovate, moderately arched; wings shorter, the blade oblong, acutish, with a large reflexed basal auricle; keel-petals nearly as long as the keel, the blades lunate, rounded at the apex ; pod crescent-shaped, about 3 cm. long, 1 cm. thick, and 5-7 mm. wide, crosswrinkled , white-strigose with somewhat kinked hairs.
Type locality: Copper Mine (west of St. George), Utah. Distribution: Northwestern Arizona and southwestern Utah.

Annual, Perennial, Herbs, Stems woody below, or from woody crown or caudex, Taproot present, Nodules present, Stems very short, acaulescent or subacaulescent, Stems prostrate, trailing, or mat forming, Stems less than 1 m tall, Stems solid, Stems or young twigs sparsely to densely hairy, Stems with 2-branched hairs, dolabriform, 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, Inflorescences racemes, 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 na rrow, 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 humistrate, lying on the ground, Fruit tardily or weakly dehiscent, Fruit oblong or ellipsoidal, Fruit strongly curved, falcate, bent, or lunate, Fruit fleshy, Fruit exserted from calyx, Fruit beaked, Fruit glabrous or glabrate, Fruit hairy, Fruit 11-many seeded, Seeds cordiform, mit-shaped, notched at one end, Seed surface smooth, Seeds olive, brown, or black.

Astragalus amphioxys, common name crescent milkvetch, is a plant found in the American southwest.