Astragalus malacus

  • Title

    Astragalus malacus

  • Author(s)

    Rupert C. Barneby

  • Scientific Name

    Astragalus malacus A.Gray

  • Description

    152. Astragalus malacus

    Low, rather stout, with a thickened, obconical root-crown or shortly forking caudex, the stems and herbage thinly to quite densely hirsute with fine, horizontally spreading and ascending hairs up to 1.3—2.7 mm. long, green or subcanes- cent, the leaflets commonly bicolored, brighter green and sometimes medially glabrescent above; stems several, erect and incurved-ascending, 2.5—20 (25) cm. long, the lower internodes inhibited and concealed by imbricated stipules, only 1—6 distal ones developed; stipules 7—17 mm. long, membranous or the uppermost thinly herbaceous, several-nerved, the lowest ovate to ovate-acuminate, amplexicaul but free, the upper ones narrower, broadly lanceolate to lance- acuminate; leaves 4—15 cm. long, all petioled, with (7) 11—19 (21) oblong obovate, obovate-cuneate, or elliptic, obtuse, retuse, or rarely subacute, flat or loosely folded leaflets 5-15 (20) mm. long; peduncles erect or incurved-ascending, sometimes reclinate in fruit, commonly stout, 4-11 cm. long; racemes 9-35- flowered, loose or early becoming so, the flowers at first anthesis ascending, declined in age, the fruits secund, the axis 2-10 (15) cm. long in fruit; bracts membranous, narrowly lance-acuminate, 4-9 mm. long; pedicels at anthesis 1 mm. long or less, in fruit arcuate, thickened, (0.7) 1-3 mm. long; bracteoles 2, often conspicuous; calyx 8.6-13 (14) mm. long, hirsute with black largely black or rarely with white or largely white hairs, the oblique disc 1-1.6 (2) mm. deep, the membranous, often purplish, cylindric tube 7-9 mm. long, 2.8-3 (4.5) mm. in diameter, the narrowly lanceolate teeth 1.6-4 (5) mm. long, petals reddish-violet with paler claws and pale, striate lozenge in the banner; banner recurved through ± 45°, 15-19 (21) mm. long, the long-cuneate claw expanded into a rhombic-ovate blade 5.5—10 mm. wide; wings 13.8—16 (20.5) mm. long, the claws 7.6-8.7 (11) mm., the linear-oblong or -lanceolate, obtuse, nearly straight blades 7.3—9 mm. long, 2-2.7 mm. wide; keel 12.3-14.5 (16) mm. long, the claws 7.5-8.6 (10) mm., the obliquely half-obovate blades 5.3-6.5 mm. long, 2.4-3.6 mm. wide, gently incurved through ± 80° to the rounded apex; anthers 0.55-0.7 (0.75) mm. long; pod reflexed, stipitate, the stout stipe 1-3 mm. long (concealed by the marcescent calyx and easily overlooked), the body narrowly oblong or oblong-elliptic in profile, shallowly crescentic or evenly incurved through nearly half a circle, 1.8-3.8 cm. long, 4.5-6 mm. in diameter, cuneately contracted at base, or at both ends, but sometimes long-acuminate distally, cuspidate at apex, triquetrously compressed with acute ventral and rounded lateral angles, the shallowly grooved dorsal face narrower than the nearly flat lateral ones, the rather thin, scarcely fleshy, green but often red- mottled valves becoming stiffly papery and stramineous in age, hirsute with spreading, lustrous, straight but sometimes twisted hairs up to (1) 1.5-2.8 mm. long, inflexed as a complete septum; dehiscence apical and downward through the ventral suture, after falling; seeds brown or greenish-brown, pitted or wrinkled, 3-3.7 mm. long.—Collections: 55 (vii); representative: Peck 25,201 (RSA); W. H. Baker 10,131 (ID, RSA); Maguire & Holmgren 26,257 (NY, RSA, UTC); Ripley & Barneby 5815, 5974, 5661 (RSA); Duran 3244 (CAS, DAV, DS, NY, OB, WIS, WS).

    Dry rocky slopes, bluffs, and canyon benches, in stiff clays or light sandy soils, mostly on basaltic, perhaps rarely granitic bedrock, among sagebrush or in piñon forest, mostly 4000-7500 feet, but descending along the Snake River as low as 2600 feet, widespread and locally plentiful along the east base of the Sierra Nevada from Esmeralda County, Nevada, and Mono County, California, north through western Nevada to Lassen County, California, thence, becoming rarer, northeast into southeastern Oregon and east to the lower Snake River Plains in southwestern Idaho.—Map No. 62.—Late April to June (July).

    Astragalus malacus (soft, of the vesture) Gray in Proc. Amer. Acad. 7: 336. 1867.— "Nevada, near Carson City, Dr. C. L. Anderson."—Lectotypus: Anderson 26, collected "February 23, 1864," GH! isotypus, numbered "26" but dated "February, 1866," US! paratypi, Anderson 307, GH, in 1864, MO, and in 1865 NY!—Tragacantha malaca (Gray) O. Kze., Rev. Gen. 946. 1891. Hamosa malaca (Gray) Rydb., Fl. Rocky Mts. 496, 1063. 1917 ("malacra").

    Astragalus obfalcatus (inversely sickle-shaped, of the pod) A. Nels. in Bot. Gaz. 54: 411. 1912.—"Secured by Macbride (No. 1023) ...on Reynolds Creek, Owyhee County, July 3, 1911 (full fruit, flowers not seen), and by Nelson and Macbride (No. 1119), at King Hill... July 15, 1911."—Holotypus, Macbride 1023, RM! paratypus Macbride (not Nelson & Macbride) 1119, RM!—A. malacus var. obfalcatus (A. Nels.) Jones, Rev. Astrag. 227, Pl. 57. 1923.

    In its area of dispersal the shaggy milk-vetch, A. malacus, is instantly recognized by its vesture of long, straight, divaricate or widely ascending hairs (mostly over 1.5 mm. long), by the unusually long stipules and bracts of a pallidly membranous texture, and by the narrow, eventually declined and secund, reddish-violet flowers. A few sympatric Argophylli of similar growth-habit are pubescent with equally long, although commonly denser and often curly hairs; but in these species the raceme is fewer-flowered, and the flowers themselves remain erect as do the humistrate pods, while the latter are never bilocular or trigonously compressed. The long, lustrous hairs, which adorn the handsome, crescentic, usually red-mottled pod of A. malacus, are remarkable for their enlarged beadlike or bulblike bases. The pod itself, of which the beak below its terminal cusp varies from triangular to long-acuminate as viewed in profile, is in form like that of the next species, A. chamaemeniscus; but when fully ripe it is more strongly compressed laterally, the dorsal face being perceptibly narrower than the other two and narrowly although not deeply grooved. The populations of the shaggy milk-vetch found at low elevations along the Snake River in Idaho, one of which furnished the typus of A. obfalcatus, do not differ substantially from the specific norm. The species is often grazed, but reportedly is sometimes injurious to stock (Moore & Franklin 31, NA).