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

333g. Astragalus Nuttalianus var. imperfectus

Always slender, the prostrate or weakly ascending (when solitary, erect) stems 2-30 (45) cm. long, the herbage strigulose with rather stiff, straight, appressed or ascending, lustrous hairs up to 0.55-0.9 (1) mm. long, the leaflets greenish-cinereous or canescent, pubescent on both sides but sometimes thinly so above; leaves 1.5-4.5 (5.5) cm. long, with 7-11 (13) broadly to narrowly elliptic or oval leaflets 2-10 mm. long, all acute, subacute, or rounded at apex, those of the lower leaves sometimes broadest; peduncles (1) 2-7 (8) cm. long, mostly longer (or some early, 1-flowered ones shorter) than the leaf; racemes 1-4-flowered, the axis (0) 2-10 mm. long in fruit; calyx 3.2-4.5 mm. long, strigulose or hirsutulous with appressed or narrowly ascending, white or black and white hairs up to (0.35) 0.5-0.8 mm. long, the tube 1.9-2.8 mm. long, 1.1-1.8 mm. in diameter, the lance-subulate teeth 1-1.7 (2) mm. long; petals whitish or faintly lilac-tinged; banner 4.1-6.5 (7.3) mm. long, 2.2-4.5 (4.8) mm. wide; wings 3.8-5.6 (6.2) mm. long; keel 4.1-5.4 (5.9) mm., the claws 1.9-2.4 (2.8) mm., the blades obliquely triangular or lunately half-elliptic, (2.2) 2.6-3.4 mm. long; pod as in var. austrinus externally, (1) 1.2-2.1 cm. long, 1.9-3.1 mm. in diameter, gently incurved at or near the base and often straight or nearly so distally, the valves glabrous or strigulose with hairs up to 0.25-0.5 (0.6) mm. long, the septum varying from complete and up to 1.5 mm. wide to a rudimentary wing in the lower half of the pod; ovules 12-16.—Collections: 53 (vii); representative: Clokey 8712 (CAS, NA, NY, OB, SMU, TEX, WIS, WS, pod pubescent, septum subobsolete), 8716 (CAS, NY, WS, pod pubescent, septum complete); Ripley & Barneby 3338 (CAS, RSA, pod glabrous, septum subobsolete); Wiegand & Upton 3615 (NY, pod glabrous, septum broad).

Open sandy or gravelly flats, hillsides, and washes, about 900-5200 (in Death Valley up to 6400) feet, with Larrea, sahuaro, and (northward) Joshua-tree, on granite and limestone, locally abundant over the deserts drained by the lower Colorado and Gila Rivers, eastern Mohave Desert, California to southwestern Utah (Washington County, in the Virgin Valley), southeast to Pima County and Sonoita Valley in Santa Cruz County, Arizona, west in California to the Little San Bernardino Mountains; apparently in the Cucopa Mountains, northeastern Baja California; collected once (possibly adventive) in Great Salt Lake (Antelope Island), northern Utah.—Map No. 150.—March to June.

Astragalus Nuttallianus var. imperfectus (Rydb.) Barneby in Leafl. West. Bot. 3: 109. 1942, based on Hamosa imperfecta (incomplete, of the septum) Rydb. in Bull. Torr. Club 54 : 329. 1927—"Nevada: Rhyolite, Nye County, May 17, 1909, Heller 9637 ... "—Holotypus, NY!

The var. imperfectus is very closely related to var. austrinus from which, as we have seen, it is not clearly differentiated in central Arizona. Northward and westward, however, it may be recognized by its deeply campanulate calyx with comparatively short teeth which lack the long, stiff, shining trichomes so characteristic of vars. austrinus and trichocarpus. As in var. austrinus the pod varies from one colony to the next in being glabrous or strigulose; the latter is the much commoner of the two states, whether the septum be present or lacking within. The variety was originally drawn to include, as was Hamosa imperfecta, only those forms with unilocular pods. In reality the legume is never fully unilocular, for although the septum may be truly obsolete in the upper two thirds, at least a rudiment persists in the incurved lowest third or quarter. The subunilocular phase of var. imperfectus is about equally common and has almost the same range as the bilocular one in Utah, Nevada, and California, but it seems to be absent in Arizona southward from Mohave County. Externally the pods of the two phases are identical, as are all other details of the plants, and the nomenclaturally typical, imperfect phase is here considered a minor variant. The variety seems to be morphologically confluent with var. cedrosensis southward. There is one collection of doubtful identity, with the calyx o var. imperfectus and some emarginate leaflets in the lower leaves quite suggestive of var. cedrosensis, from as far north as the Panamint Mountains (Coville & Funston 513, NY). The record from Salt Lake was made by Sereno Watson on King’s Exploration and has not been confirmed, to my knowledge, in latter years. The plant was very likely introduced, possibly by livestock from the Mormon settlements on the Virgin River in southwestern Utah.