Astragalus Serenoi var. Serenoi

Open places on dry hillsides and on canyon benches, in gravelly, alkaline clay soils, associated with sagebrush and piñon-juniper forest (4700) 5000-7400 feet, local but forming colonies, western Nevada, from the West Humboldt Mountains, Pershing County, south to the Palmetto Range and White Mountains in Esmeralda County and the Inyo and Cottonwood Mountains in Inyo County, California.—Map. No. 68.—May to July, the fruit often persisting over winter on stiff, dead stems.

Astragalus Serenoi (O. Kze.) Sheld. in Minn. Bot. Stud. 1: 130. 1894, based on Tragacantha Serenoi (Sereno Watson, 1826-1892, botanist on King’s Exploration of the 40th Parallel, 1869-70) O. Kze., Rev. Gen. 941. 1891, a substitute for A. nudus (naked, of the pod) Wats., Bot. King 74. 1871 (non A. nudus Clos, 1846).—"West Humboldt Mountains, Nevada; 5000 feet altitude; May, June. 280."—Holotypus, collected in 1868, US! isotypi, GH, NY!—A. oblatus (flattened at the poles, of the pod) Sheld. in op. cit. 21. 1894, an independent substitute for A. nudus Wats. non Clos. A. Watsonianus (Sereno Watson) Spegazz. in Anal. Mus. Nac. Buenos Aires 7: 265. 1902 (non A. Watsonianus Sheld., 1894), a further substitute for the same. Brachyphragma Serenoi (O. Kze.) Rydb. in Amer. Jour. Bot. 16: 205, Pl. XVII, fig. S. 1929.

Astragalus Shockleyi (William Hillman Shockley, 1855-1925) Jones in Proc. Calif. Acad. Sci. II, 5: 659. 1895.—"Fish Lake Valley, Nevada. Shockley, July 20, 1886."—Holotypus, Shockley 527, CAS! isotypi, NA, ND! Brachyphragma Shockleyi (Jones) Rydb. in N. Amer. Fl. 24: 400. 1929.

Astragalus canonis (of a canyon) Jones, Contrib. West. Bot. 8: 15. 1898.—"Big Indian Canyon near Hawthorne, Nev., May 27, 1897 ... "—Holotypus, POM! isotypi, MO, NY, POM (3 sheets), US (2 sheets)!

The naked milk-vetch, var. Serenoi, a tall astragalus readily recognized by its wiry, bushy- branching habit of growth, few, narrow, distantly disposed leaflets usually silvery above and greenish beneath, and loose racemes of rather long but narrow, purple flowers giving rise to plumply or narrowly oblong, subterete fruits of fleshy, ultimately ligneous texture, is conspicuously variable only in the length and amplitude of the pod. The plants described by Jones as A. Shockleyi and A. canonis represent the extremes of variation, the former having a relatively short and narrow, the latter an exceptionally large and broad pod; but neither can be detached from the uninterrupted series of intermediate states of which Watsons original A. nudus forms a part. The populations of var. Serenoi found near the east base of the Wassuk Range above Walker Lake, from which the typus of A. canonis was taken, are unusually vigorous and some have relatively broad, linear-lanceolate rather than truly linear leaflets. In his summary account of the genus Jones (1923, p. 150) reduced A. Shockleyi to the synonymy of A. Serenoi and suggested that A. canonis was probably no more than a form of the same, an opinion borne out by subsequent exploration of western Nevada. The differential characters attributed by Rydberg (1929, p. 399, in clave) to Brachyphragma Shockleyi have proved of no practical use. The variation in the fruit is well illustrated by Jones s figures on Plates 32 and 74 of his Revision.