Astragalus conjunctus

  • Title

    Astragalus conjunctus

  • Authors

    Rupert C. Barneby

  • Scientific Name

    Astragalus conjunctus S.Watson

  • Description

    169. Astragalus conjunctus

    Subacaulescent or shortly caulescent, with a stout, woody, pluricipital taproot and shortly forking, cespitose caudex, thinly strigulose with fine, appressed and subappressed, mostly straight hairs up to 0.35-0.55 mm. long, the herbage greenish or subcinereous in youth, the base of the stems often, and the upper leaflet- surface nearly always glabrous; stems several or numerous, robust or quite slender, erect and stiffly ascending in clumps, 1—10 (14) cm. long, simple above the immediate base, composed of (1) 2—5 developed internodes (up to 6 cm. long, mostly shorter), the whole axis shorter than the inflorescences; stipules scarious, 3—10 (11) mm. long, the lowest connate into a bidentate sheath, this often ruptured in age by the developing stem, the median and upper ones narrower, very shortly connate or cauline, with lanceolate or deltoid-acuminate blades beset with a few minute peg- or tack-shaped processes; leaves erect, mostly clustered in a subradical tuft, (6) 10-30 cm. long, with stiffly wiry petiole and rachis and (9) 13-25 (31) distant and often scattered, linear-oblong, -elhptic, lanceolate, or subfiliform, obtuse, acute, rarely retuse, flat or involute leaflets 3-23 mm. long, the terminal one sometimes continuous with the rachis, the lateral ones readily disjointing in age; peduncles commonly stout, stiffly erect or divergent in fruit, 1-3.3 dm. long, a little shorter to much longer than the leaves; racemes loosely 7-17 (20)-flowered, the flowers at full anthesis ascending or loosely spreading (but not nodding), the axis elongating, (3) 4—12 (15) cm. long in fruit; bracts membranous, narrowly ovate to linear- or lance-acuminate, 2—4.5 mm. long; pedicels at anthesis slender, 1-2 mm. long, in fruit erect or narrowly ascending, clavately thickened, 2-4.5 mm. long; bracteoles nearly always 2; calyx (7) 8.5-12 mm. long, strigulose-pilosulous with black or largely black hairs up to 0.45-0.9 mm. long, the oblique disc 1-1.5 mm. deep, the membranous, cylindric or subcylindric tube (5.7) 6-9.2 mm. long, 2.5-4 mm. in diameter, the subulate teeth 1.3-3 (4) mm. long, the ventral pair commonly broadest and directed away from the broad ventral sinus, the whole becoming scarious, fragile, irregularly circumscissile; petals whitish with purple keel-tip, or with banner and wing-tips also suffused with lilac-blue or purple; banner recurved through 45°, oblanceolate or broadly rhombic-oblanceolate, emarginate, 16-25.5 mm. long, 6.7-10.5 mm. wide; wings 14.2-22.3 mm. long, the claws 7—11.5 mm., the oblong-oblanceolate, obtuse or obscurely emarginate, straight or slightly incurved blades 8.3-13 mm. long, (1.8) 2.5-4 mm. wide; keel 11.6-17.5 mm. long, the claws 6.3-10 mm., the half-obovate blades (5.7) 6.2-8.5 mm. long, 2.5-3.8 mm. wide, abruptly incurved through 80-90° (rarely less) into the bluntly deltoid apex; anthers (0.6) 0.7-0.85 (0.95) mm. long; pod erect, sessile, oblong-ellipsoid to narrowly oblong-ovoid, 1.2-2.5 cm. long, 5-8 mm. in diameter, straight or a trifle incurved, obtuse at base, contracted distally into a triangular-cuspidate, laterally compressed beak, otherwise obcompressed, with flattish ventral face keeled by the prominent, cordlike suture, and almost flat to widely and openly grooved dorsal face, the fleshy, green, glabrous valves becoming leathery or subligneous, stramineous, transversely rugulose and wrinkled lengthwise, commonly inflexed as a partial septum up to 1.4 mm. wide, but the septum sometimes vestigial or obsolete; ovules 23—30; seeds brown, chestnut-brown, or olivaceous, smooth but dull, 2.4—3.3 mm. long.—Collections: 59 (vi); representative: Cusick 2374 (ND, ORE); Maguire & Holmgren 26,637 (CAS, NY, UTC, WS); Cronquist 6279 (ID, NY, SMU, TEX, WS), 6957 (ID, NY, RSA); Ripley & Barneby 6115 (CAS, RSA), 6632 (CAS, RSA).

    Stony hilltops, rough meadows, brushy hillsides and canyon benches, in grassland, sagebrush desert, and ascending rarely into the lower edge of the xeric pine forest, usually, perhaps exclusively on basaltic bedrock, (1600) 2000—5100 feet, common and locally plentiful in north transmontane Oregon, from the Blue Mountains in Baker County west to the Deschutes River, south to the Malheur Valley, Steens Mountain, and east into Owyhee County, Idaho.—Map No. 69. Mid- April to June, the fruit persisting into winter.

    Astragalus conjunctus (joined together, of the lower stipules) Wats. in Proc. Amer. Acad 17: 371. 1882.—"In John Day Valley, Oregon (J. Howell, in May, 1880) and on sterile rocky ridges in Baker County, by W. C. Cusick, 1881."—Holotypus, Howell 263 GH! isotypi, from "Muddy Station, John Day Valley," ORE, WS! paratypi, Cusick 948, GH, ORE (from "s. of Baker City," fide Cusick)!—A. reventus var. conjunctus (Wats.) Jones, Contrib. West. Bot. 10: 61. 1902. Phaca conjuncta (Wats.) Piper in Contrib. U.S. Nat. Herb. 11 (Fl. Wash.). 373. 1906. Tium conjunctum (Wats.) Rydb. in N. Amer. Fl. 24: 393. 1929.

    The growth-habit of the section, distinctive except in so far as it is shared by some Reventi-arrecti, is well illustrated by the average plant A. conjunctus. The proper stems are composed of several inhibited lower internodes succeeded by one to four more strongly developed ones, and in consequence most of the leaves are disposed in a loose basal tuft. The leaves themselves are comparatively long, and the narrow distant or at least well-spaced leaflets give a peculiar sparse aspect to the herbage. The peduncles, of which the uppermost is often as thick as the true stem at at times may appear falsely terminal because of atrophy of the bud beyond it are held stiffy erect at anthesis; together with the loose racemes they make up more than half (in most cases much more than half) the plant's total height. The general appearance suggest some acaulescent species of Oxytropis such as O. Lambertii Pursh, and the resemblance is accentuated in A. conjunctus and in the closely related A. hoodianus by the strictly erect pods of narrowly ellipsoid form.

    The basalt milk-vetch, A. conjunctus, is mostly easily recognized in the flowering state, for the long, narrow blossoms with their cylindric calyx and usually lilac- or purple-tinged petals provide the most readily observed diagnostic characters. Mature specimens are likely to be confused with the narrow-fruiting forms of A. reventiformis, but this is apparently confined to the inner slope of the Cascades in Washington, well north of the range of A. conjunctus. The pod of the basalt milk-vetch varies a good deal in length and diameter and in development of the septum, which is sometimes lacking altogether, but the variations do not conform to any geographical pattern and must by attributed to inherited instability. Exceptionally large flowered plants (e. g. Peck 26,188, RSA) have been collected several times in the lower John Day Valley, but they do not form uniform or exclusive colonies.

    Two collections from Wasco County, Oregon (near Boyd, C. E. Hill 18, 19, WS), in the hill country south of the Columbia River, show combined in one plant the narrow, shorttoothed calyx of A. conjunctus and the pubescent pod of A. hoodianus, a species which becomes common a few miles northward along the river. These specimens suggest introgression between the two species, but are perhaps no more than a minor variant of A. conjunctus. The fruit of the related A. Leibergi varies from glabrous to strigulose, sometimes in a colony of otherwise like plants.