Astragalus preussii var. laxiflorus
Proc. Amer. Acad. Arts 13: 369. 1878.
Plants sometimes flowering first year, (10–)30–53 cm. Leaves 4–15 cm; leaflets (7 or)9–15(or 17), blades broadly obovate to suborbiculate, 6–18(–23) × 3–11(–13) mm, apex obtuse or truncate and apiculate. Peduncles (6–)8–15 cm. Racemes lax, (8–)15–24-flowered; axis 9–19.5 cm, slightly elongated in fruit. Flowers: calyx 6.4–8.5(–9.4) mm, tube color strongly contrasting with corolla, 5.5–7 mm, lobes 1.5–1.9 mm; corolla usually pale greenish yellow, less commonly suffused with pale purple; banner 14–17.5 mm. Legumes ovoid to ellipsoid, length usually less than 3 times width, 17–20(–25) × 7–10(–11) mm, abruptly contracted at base; sessile or subsessile. 2n = 24.
Phenology: Flowering late Feb–May.
Habitat: Creosote bush and desert-holly communities, on gypsum soils.
Elevation: 600–2500 m.
Distribution
Ariz., Calif., Nev., Utah.
Discussion
Variety laxiflorus is restricted to the vicinity of the juncture of Mohave County in Arizona, Clark County in Nevada, and Washington County in Utah; it is not known from modern Utah collections. R. C. Barneby (1964) suggested that in the widely disjunct station on the western edge of the Mojave Desert at Lancaster, the plants recognized as Astragalus crotalariae var. davidsonii, though similar in habit and fruit, may represent an independent origin because of the small flowers and fewer ovules. There are no recent collections, and that population is likely extinct.
Selected References
None.