Astragalus lentiginosus var. stramineus

Short-lived perennial, sometimes flowering the first season, strigulose with appressed and ascending hairs up to 0.4—0.6 mm. long, the stems silvery-canescent, the herbage silvery or more often greenish, the leaflets glabrous or medially glabrescent above; stems 1.2-3.5 (4) dm. long; leaves (2.5) 4—11 (13) cm. long, with (9) 11-15 broadly oblanceolate or obovate-cuneate, openly notched, flat leaflets (3) 5-18 mm. long; peduncles 3.5-9 cm. long; racemes loosely or remotely 15-25 (30)-flowered, the flowers ascending, the axis 5-12 cm. long in fruit; calyx 5-6.6 mm. long, white-strigulose, the tube 3.8—4.5 mm. long, 2.1-2.5 mm. in diameter, the teeth 1.2—2.1 mm. long; petals pale purple or lilac, early fading brownish or ochroleucous after drying; banner 11—12 mm. long, 5—6.2 mm. wide; wings 10—11.2 mm. long, the blades 6.5—7.2 mm. long; keel 10—10.4 mm., the blades about 6 mm. long; pod obliquely ovoid-acuminate, (1) 1.7—2.6 cm. long, 1-1.6 cm. in diameter, bladdery-inflated, the incurved, triangular or lance- acuminate, distally unilocular beak (2) 3—7 mm. long, the rather firmly papery, greenish but usually mottled, strigulose valves becoming stramineous, the septum complete, 3-4.5 mm. wide, the funicular flange 0.7-1 mm. wide; ovules 20-26.— Collections: 9 (i); representative: Palmer 116 in 1877 (GH, NY); Peebles & Parker 14,767 (GH, NY, SAC); Eastwood & Howell 9037 (CAS); Maguire & Blood 4415 (F, POM, UC); Ripley & Barneby 4295 (RSA).

Sandy and gravelly valley flats and dunes, ± 2000—3000 feet, locally plentiful in the lower Virgin Valley, in Mohave County, Arizona, and adjoining Clark County, Nevada; reported, perhaps incorrectly, from "south-eastern Utah, but without precise locality.—Map No. 131.—April and May.

Astragalus lentiginosus var. stramineus (Rydb.) Barneby in Leafl. West. Bot. 4. 122. 1945, based on Cystium stramineum (straw-colored) Rydb. in N. Amer. Fl. 24. 409. 1929. "Type collected in southeastern Utah in 1870, E. Palmer... "—Holotypus, NY! isotypus, US!

The var. stramineus is nearly related to var. yuccanus and var. variabilis. It is obviously, even if only superficially distinguished from the first by its lilac-purple flowers, but should perhaps be united with the polymorphic var. variabilis. The latter differs ideally but not quite consistently in having calyx-teeth shorter in relation to the tube. It enjoys a range of dispersal in the central and western Mohave Desert separated from that of var. stramineus by an extensive tract of territory in which the only freckled milk-vetch is the much smaller-flowered var. Fremontii. The var. stramineus has an intangible individuality of aspect and probably arose independently of var. variabilis.

The description of var. stramineus has been prepared principally from examples of the populations found on the sandy floor of the lower Virgin River Valley around Beaver Dam, Littlefield, and Mesquite. As mentioned elsewhere (Barneby, 1945, p. 122) the typus of Cystium stramineum is a fragmentary specimen simply labeled "Southeast Utah" and differs in having longer and straighter pubescence and notably bicolored leaflets. The color of the long-faded petals is not known for certain, but I have assumed them to have been purple as in the plant collected by Capt. Bishop in 1874 (POM), the one specimen seen that really closely matches the original C. stramineum. Bishop’s plant is labeled "southern Utah" and may well have come from the Kanab region, or from adjoining northern Arizona, although the very glabrous var. vitreus is the freckled milk-vetch dominant around the foot of the escarpment eastward from Zion Park. A modern collection from a precise locality of truly typical C. stramineum will be awaited with interest, for final disposition of the epithet is contingent upon this rediscovery.