Monographs Details: Astragalus emoryanus (Rydb.) Cory var. emoryanus
Authors:Rupert C. Barneby
Authority: Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(2): 597-1188.

323a. Astragalus Emoryanus var. Emoryanus

Peduncles homomorphic or nearly so, all equaling or surpassing the leaf; vesture mostly appressed or subappressed, distinctly shorter than that of var. terlinguensis where the two varieties coincide in range; pod as given in the key.— Collections: 52 (v); representative: Wooton 3842, 3870 (NMC); Earle 589 (NY); Ripley & Barneby 4212 (RSA), 11,146 (CAS, NY, RSA, US); Jones 28,191 (CAS, POM), 29,319 (MO, POM); E. J. Palmer 11,686 (NY); Johnson & Barkley 16,243 (GH, NY, TEX); Webster & Barkley 13,504 (TEX), 13,504A (MO).

Dry stony hillsides, canyons, sandy flats and washes, gravel bars of intermittent streams, sometimes in disturbed soil along highways, strongly but not exclusively calciphile, locally plentiful in the Rio Grande Valley and adjoining hill-country in southern New Mexico and trans-Pecos Texas, where associated with Larrea, mesquite-grassland, or juniper forest between 2000 and 5600 (6000) feet, extending north and up to 7000 feet in the Sandia Mountains into north- central New Mexico, south to northern Chihuahua, and descending southeast and down to 100 feet in scattered stations on both banks of the Rio Grande to the Gulf Coast in southern Texas and Tamaulipas, and south to the foothills of the Sierra Madre Oriental in Nuevo Leon and southeastern Coahuila; apparently greatly isolated in northwestern Arizona (Grand Canyon of the Colorado River; near Beaver Dam).—Map No. 146.—February to June.

Astragalus Emoryanus (Rydb.) Cory in Rhodora 38: 406. 1936, based on Hamosa Emoryana (William Hemsley Emory, 1811—1887, Lieutenant U. S. Army, in command of one of the Mexican Boundary Survey parties) Rydb. in Bull. Torr. Club 54: 237. 1927.—"Wright also collected well-developed specimens at El Paso (no. 1359). This number as represented in the Torrey Herbarium I have taken as the type."—Holotypus, collected by Charles Wright in 1852, NY! isotypi, GH, MO!

Hamosa montereyensis (of Monterrey, Nuevo Leon) Rydb. in Bull. Torr. Club 54: 326. 1927.—"The type was collected at Monterey, Nuevo Leon, February 1880, Palmer 237 (Gray Herbarium)."—Holotypus, GH!

The typical form of the Emory milk-vetch is a slender, few-stemmed plant with neat, obovate or obcordate leaflets less than a centimeter long, ashen at least beneath and marginally with subappressed hairs. It is the phase encountered most commonly in New Mexico and far western Texas at middle elevations and recurs, possibly as a result of chance introduction, in the Grand Canyon, Arizona, and in Milam and Bastrop Counties on the coastal plain in east- central Texas. Populations of perennant plants, germinating in fall and flowering in favorable years over a long period lasting from spring into late summer of the ensuing season, occur in the foothills of the Guadalupe Mountains in Culberson County, Texas, and in the White and Sandia Mountains in New Mexico. These eventually form wide mats of freely branching stems beset with an extraordinary profusion of small, gaily colored purple blossoms, at first sight very distinct, but precisely typical in the form of the flower and fruit and, when young or when starved of moisture, reverting to the more ordinary type. Along the lower Rio Grande, largely separated from the foregoing by the Big Bend country where the Emory milk-vetch is represented by its endemic var. terlinguensis, the predominant phase of the species is coarser and leafier and more thinly pubescent with slighdy shorter hairs. Plants of this nature from Zapata County (Ripley & Barneby 9050, RSA) grew in moist sand of a creek bed and their unfamiliar appearance was attributed, perhaps wrongly, to the environment; most material from the region is similar and may represent a distinct variety. In Nuevo Leon and eastern Coahuila there is another seemingly trivial variant of A. Emoryanus, distinguished by a flower with wings as long as the banner or nearly so and consequently a certain individual facies. A plant of this sort furnished the typus of Hamosa montereyensis. The racial situation in this region deserves attentive study.

The history of A. Emoryanus is rather curious, but as it has been told elsewhere in some detail (Barneby, 1956, p. 493) there is place here for only a summary sketch. A common species along the Mexican boundary, it was collected by most of the botanists active in the Rio Grande Valley in the early days of exploration, but was consistently confused with sympatric forms of A. Nuttallianus, in the first place by Gray, and by all succeeding students of the genus. Gray’s practice of mixing supposedly conspecific materials from different localities and distributing these under a common label promoted subsequent confusion of critical species; the annual astragali collected by Charles Wright and the Boundary Survey parties were mixed in this way, and A. Emoryanus was unnecessarily lost to sight for a century. The species was finally described only by accident. It is clear from Rydberg’s discussion that the substance of his Hamosa Emory ana was almost wholly the glabrous-fruiting variant of A. Nuttallianus var. austrinus, although the specimen that he selected as holotypus is the species treated here. Despite the contradictions involved, the name remains attached in Astragalus to the precisely specified typus.