Astragalus linifolius

  • Title

    Astragalus linifolius

  • Authors

    Rupert C. Barneby

  • Scientific Name

    Astragalus linifolius Osterh.

  • Description

    115. Astragalus linifolius

    Junceous, apparently leafless perennial, closely resembling A. toanus in habit, the growing tips and inflorescence thinly strigulose with appressed and subappressed hairs up to 0.5-0.6 mm. long, the stems yellowish-green; stems ± 3.5-4 dm. long, shortly subterranean at base, bearing 1-2 branches well below the middle, abruptly flexuous distally; stipules dimorphic, the lowest papery-membranous, several-nerved. 5 mm. long, connate-amplexicaul into a bidentate sheath, the upper ones 2.5-4mm. long, herbaceous, connate at base only, with triangular-subulate, erect or deflexed blades, all glabrous dorsally; leaves (3) 4—12 cm. long, mostly reduced to the naked rachis, some lower ones bearing near the middle a single pair of obovate or linear-involute, decurrent leaflets 2—12 mm. long; peduncles stout, erect (appearing like a continuation of the stem), 1—2.5 dm. long; racemes loosely or remotely 6— 10-flowered, the uppermost ones 2—3-flowered, the flowers ascending, the axis early elongating, (1.5) 3—9 cm. long in fruit; bracts pallid but firm, prominently nerved, triangular-subulate, 2—3 mm. long; pedicels ascending, at anthesis 0.5—2 mm., in fruit thickened, 1.5—3.5 mm. long; bracteoles 1—2, sometimes sub- obsolete; calyx 6.6—7.8 mm. long, white-strigulose, the disc ±1.5 mm. deep, the campanulate tube 5—5.2 mm. long, 3.7—3.8 mm. in diameter, the subulate teeth 1.4—2.8 mm. long, the whole becoming papery-membranous, fragile but marcescent; petals, according to Osterhout’s field note, "white, the keel with a small purple tip ; banner recurved through ± 45°, broadly rhombic in outline, 14.6—18 mm. long, 9—9.5 mm. wide; wings 12.4—16.5 mm. long, the claws 4.7—6.3 mm., the linear- oblanceolate, obtuse, almost straight blades 8.4—11.2 mm. long, 2.6—3.2 mm. wide; keel 11.3—12.3 mm. long, the claws 5.3—6.2 mm., the lunately half-elliptic blades ± 6.5 mm. long, 3.1 mm. wide, incurved through ± 80° to the bluntiy triangular apex; anthers 0.6-0.7 mm. long; pod erect, sessile, narrowly oblong-ellipsoid, nearly straight, 1.2—1.7 cm. long, 4.5—6 mm. in diameter, broadly cuneate at base, abruptly contracted at apex into a rigid, subulate cusp 1.5—2 mm. long, a trifle laterally compressed, bicarinate by the thickened, salient sutures, the faces convexly rounded, the fleshy, green, glabrous valves becoming ligneous, stramineous, cross-reticulate and wrinkled lengthwise, not inflexed; dehiscence apical and half-way down through both sutures; ovules 18-20; seeds not seen.—Collections: 2 (o); representative: Osterhout (from the type-station) in 1921 (NY, RM).

    Low gullied hills, ± 4700-5000 feet, known only from the type-locality in the Grand River Valley near Grand Junction, Mesa County, Colorado.—Map No. 49. —May and June.

    Astragalus linifolius (flax-leaved, but probably intended to mean linear-leaved) Osterh. in Bull. Torr. Club 55: 75. 1928.—"Collected on the hills some six miles across the Colorado River from Grand Junction, 18 June 1926; no. 6557."—Holotypus, RM! isotypi, GH, NY, POM!—Ctenophyllum linifolium Osterh., l.c., nom. nud. in syn.

    The Grand Junction milk-vetch, A. linifolius, is so poorly known that reflections on its taxonomic status have little value. The species was reduced by Rydberg (1929, p. 287) to A. rafaelensis, but it seems to be at least varietally distinct in its somewhat smaller, erect pod, longer calyx-teeth, and whitish petals. It resembles A. toanus in the upright fruit and was reduced to it by C. L. Porter (1951, p. 31), but the comparatively few-flowered racemes and once again the whitish petals are different. For phytogeographic reasons a closer relationship would be expected between A. linifolius and A. rafaelensis, both native to sandstone areas at low elevations in the Colorado Basin, than between either of these and the distantly allopatric A. toanus, a species of the Great Basin which reaches its eastern known limit in Utah west of Great Salt Lake. The fruits of the three entities are essentially alike in form, and possibly they represent no more than three phases of a single, discontinuously dispersed species. Material of A. linifolius in vigorous young flowering condition is needed before the racial situation can be clarified.