Astragalus humistratus var. humistratus

  • Title

    Astragalus humistratus var. humistratus

  • Authors

    Rupert C. Barneby

  • Scientific Name

    Astragalus humistratus A.Gray var. humistratus

  • Description

    100a. Astragalus humistratus var. humistratus

    Herbage deep green or sometimes greenish-cinereous, thinly pilose-pilosulous with shorter, appressed, together with some longer, narrowly ascending hairs up to 0.8-1.5 mm. long, the leaflets glabrous above; stems prostrate, (1.5) 2-6 dm. long; stipules 2-9 (11) mm. long; leaves (1) 1.5-5.5 cm. long, often shorter than the intemodes, with 11-17 leaflets 4-14 mm. long; peduncles (2) 3-8 cm. long; racemes (5) 7-30-flowered, the axis (1) 1.5-6 cm. long in fruit; calyx (5.8) 6-7.6 mm. long, the disc 0.7-1 mm. deep, the tube 3-3.8 mm. long, 2.7-3.4 mm. in diameter, the lance-acuminate or filiform-setaceous teeth (2.5) 3-4.5 mm. long; petals greenish-white or sordidly ochroleucous, often distally suffused and veined with dull purple; banner 9.5-11.8 mm. long, the broadly obovate to rhombic-ovate or subquadrate blade 6-8 mm. wide; wings 8.7-10.7 mm. long, the claws 3.1-4.5 mm., the blades 6.2-7.4 mm. long, 2.2-3.1 mm. wide; keel 7.8-10 mm. long, the claws (2.9) 3.2-4.5 mm., the blades 4.6-6.4 mm. long, 2.4-2.8 mm. wide, incurved through about 90° to the sharply triangular, somewhat porrect apex; anthers 0.45-0.55 mm. long; pod obliquely oblong- or lance-ellipsoid, gently incurved, 14-18 mm. long, 4-6.5 mm. in diameter, dorsally sulcate downward from the base of the beak, thinly (rarely densely) strigulose; ovules (16) 18-26.— Collections: 30 (vii); representative: Metcalfe 453 (NY, NMC), 1067 (CAS, NY, NMC); Ripley & Barneby 5078 (CAS, RSA); Barneby 12,847 (CAS, RSA); Bethel, Willey & Clokey 4172 (NY); Warnock & Hinckley 7393 (SMU, SRSC, TEX); Mexia 2573 (CAS).

    Gravelly and sandy flats, open banks, sometimes on gravel bars of intermittent streams, commonly in pine forest, but descending to dry hills and mesas among piñon and juniper, chiefly on granites and basalt, 4400—8700 feet, widespread over northcentral New Mexico from the upper Canadian and Pecos to the sources of the Gila River, west into the White Mountains and Natanes Plateau in eastcentral Arizona, north just into southern Archuleta County, Colorado, and south interruptedly to the Davis Mountains in trans-Pecos Texas and into northwestern Chihuahua.—Map No. 41 A.—May to September, but most abundant after summer rains.

    Astragalus humistratus (stretched out on the ground) Gray, Pl. Wright. 2: 43. 1853.— "Pebbly bed of a stream and on hills under pine-trees, near the copper mines, New Mexico, Aug. (1003)."—Holotypus (Wright 1003), collected in 1851, GH! isotypi, BM, K, NY, PH, U&—Tragacantha humistrata (Gray) O. Kze., Rev. Gen. 945. 1891. Tmm hum,stratum Gray Rydb. in Bull. Torr. Club 32: 660. 1905 ("huministratum ). Batidophaca humistrata (Gray) Rydb. in N. Amer. Fl. 24 : 315. 1929.

    Pisophaca datilensis (of Datil, New Mexico) Rydb. m N. Amer. Fl 24: 328^ 1929-Type collected at Negrito Ranger Station, Datil Forest, New Mexico, September 22, 1919, Eggleston 16087."—Holotypus, NY!—Astragalus datilensis (Rydb.) Tidest. in Proc. Biol. Soc. Wash. 50: 21. 1937.

    The ground-cover milk-vetch, var. humistratus, is a weedy and undistinguished astragalus which forms matted growths in dry pine forest or in open spaces among piñons and junipers; it quickly colonizes disturbed ground along highways and serves to control erosion of roadside banks and cuttings. The flowers vary from greenish-white to purple, but the cyanic pigment is usually diluted with brown or yellow and therefore lurid, only rarely of amethystine hue. The plant described as Pisophaca datilensis is a characteristic specimen of var. humistratus and has nothing in common with the forms of A. (Scytocarpi) flexuosus among which it originally appeared.