Astragalus Geyeri var. triquetrus

  • Title

    Astragalus Geyeri var. triquetrus

  • Author(s)

    Rupert C. Barneby

  • Scientific Name

    Astragalus geyeri var. triquetrus (A.Gray) M.E.Jones

  • Description

    283b. Astragalus Geyeri var. triquetrus

    Always annual; leaflets (5) 7—9, broadly oblanceolate or elliptic, mostly retuse, 4—15 mm. long, pubescent on both sides, flat, the terminal one not conspicuously longer than the last pair; pod more definitely trigonous than that of var. Geyeri, openly sulcate dorsally, the valves inflexed as a narrow partial septum 0.6—1.2 mm. wide; ovules 7—11.—Collections: 3 (o); representative: Eastwood & Howell 9000 (CAS, RSA); Peebles & Parker 14,678 (NY).

    Sandy flats and washes, with Larrea, 1500-2000 feet, rare and local, along and near the lower Muddy, Virgin, and Colorado Rivers in extreme northwestern Mohave County, Arizona, and southern Clark County, Nevada.—Map No. 122. —April and May.

    Astragalus Geyeri var. triquetrus (Gray) Jones, Contrib. West. Bot. 8: 7. 1898, based on A. triquetrus (three-cornered, of the pod) Gray in Proc. Amer. Acad. 13: 367. 1878.— "Southeastern borders of Nevada, at the confluence of Muddy River with the Virgen, Dr. Palmer, 1877."—Holotypus (from "Muddy River at St. Thomas"), GH!—Phaca triquetra (Gray) Rydb. in N. Amer. Fl. 24: 353. 1929.

    The var. triquetrus is one of the rarest desert milk-vetches, known only from the Arizona Strip near Beaver Dam, from the now inundated type-station, and from the Valley of Fire near Crystal. It has been collected only seldom and in very small quantity, and nothing is known at present of potential variation within it. It is distinguished at sight from var. Geyeri by its few broad leaflets pubescent on both faces, although the habit of growth is essentially the same. The pods of the two varieties are alike in profile, but that of var. triquetrus is not only grooved along the back and semibilocular but also encloses slightly fewer seeds. In the context of the section var. triquetrus is strongly marked and may perhaps deserve its original specific status.