Astragalus preussii var. laxiflorus

  • Title

    Astragalus preussii var. laxiflorus

  • Author(s)

    Rupert C. Barneby

  • Scientific Name

    Astragalus preussii var. laxiflorus A.Gray

  • Description

    179b. Astragalus preussii var. laxiflorus

    Leaflets 11-15, broadly obovate, obtuse, or truncate and mucronulate; banner 14-17.5 mm. long.—Collections: 13 (o); representative: Clokey 5862 (CAS, NA, NY, UC, WS); Eastwood & Howell 9006 (CAS, RSA); F. W. Gould 1518 (CAS);Tidestrom 8674 (NA), 9144 (NY).

    Gravelly or sandy washes and along draws in gullied badlands, 1200-2500 feet, uncommon, lower Muddy and Virgin Valleys around the common boundary point of Nevada, Utah, and Arizona; isolated, probably on alkaline clay flats at ± 2350 feet, on the southwest Mohave Desert (near Lancaster, Los Angeles County), California.—Map. No. 72.—March to May.

    Astragalus preussii var. laxiflorus (loosely flowered) Gray in Proc. Amer. Acad. 13: 369. 1878.—"Beaverdam, on the Virgen, northeast corner of Arizona, Dr. Palmer (1877)."— Holotypus, Palmer 104 in 1877, GH! isotypi, K, MO, NY, US!—A. Preussii var. laxispicatus (with loose racemes) Sheld. in Minn. Bot. Stud. 1: 130. 1894, a superfluous substitute. Phaca laxiflora (Gray) Rydb. in N. Amer. Fl. 24: 363. 1929.

    Phaca Davidsonii (Anstruther Davidson, 1860-1932, physician, botanist, entomologist, in s. California from 1889) Rydb. in N. Amer. Fl. 24: 362. 1929.—"Type collected at Lancaster, California, May 12, 1893, A. Davidson 4... ’’—Holotypus, GH! isotypi, DS, NY, US!—A. Crotalariae var. Davidsonii (Rydb.) Munz & McB. ex Munz in Bull. S. Calif. Acad. Sci. 31: 66. 1932.

    The var. laxiflorus is distinguished from var. Preussii by its sessile pod and by the greater length of all but some depauperate, subterminal racemes. The name should perhaps be restricted to the populations found in the main area around the head of Lake Mead, which seem to be the progeny of a mutation derived from the typical phase of var. Preussii prevalent in southern Nevada. The so-called Phaca Davidsonii, isolated at a single point on the Mohave Desert 170 miles to the west, is still poorly known (from one collection, Elmer 3669, NY, beside the typus) and may represent a parallel mutation of independent origin. It resembles var. laxiflorus closely in habit and pod, but stands out as mildly remarkable for its small flower (calyx ±6.5 mm., banner ± 14 mm. long), and few (20-22) ovules. Whatever the status of this form, which has been sought vainly in recent years, it is certainly too close to var. laxiflorus to be excluded from A. Preussii sens. lat. It has been subordinated as a variety to A. Crotalariae of the Colorado Desert, but differs from this in its narrow, little-inflated, glabrous pod, almost hairless herbage, and flowers smaller by about one third.