Astragalus eurekensis

  • Title

    Astragalus eurekensis

  • Authors

    Rupert C. Barneby

  • Scientific Name

    Astragalus eurekensis M.E.Jones

  • Description

    210.  Astragalus eurekensis

    Low, tufted, strictly acaulescent, with a woody taproot and 1-several hard, turbinate crowns beset with a thatch of leaf-bases and scaly stipules, the leaves and peduncles pilose-pilosulous with rather stiff, straight or nearly straight, appressed and subappressed hairs up to (0.6) 0.8-1.4 mm. long, the herbage gray or silvery-canescent, the leaflets equally pubescent on both faces, the calyces (and sometimes the peduncles just below the flowers) hirsute with longer, spreading, white or commonly mixed black and white hairs up to (0.8) 1.2-2.5 mm. long; stipules closely imbricated, broadly lanceolate, 3-11 mm. long, at first pallid but rather firm, becoming papery, brownish, glabrescent, several-nerved; leaves (2) 4-15 cm. long, with stiff petioles and (3) 5-11 (17) narrowly elliptic, oblong- elliptic, rhombic-oblanceolate, or almost linear, acute or subacute, flat or loosely folded, readily deciduous leaflets 5-20 (25) mm. long; peduncles (1) 2.5-10 (14) cm. long, erect or incurved at anthesis, arcuate-recurved in fruit; racemes loosely but very shortly (1) 3-7-flowered, the flowers widely ascending, the axis little or not elongating, not over 1 cm. long in fruit; bracts lanceolate or linear-caudate, 4-8 mm. long, pallid but rather firm; pedicels ascending, straight or nearly so, at anthesis 1.2-2 mm., in fruit thickened, persistent, 1.5-3 mm. long; bracteoles 0; calyx 10.5-15.5 mm. long, the oblique disc 1.1-1.8 mm. deep, the cylindric (often a little constricted upward) tube (7) 8.5-10.5 mm. long, 3.7-4.5 mm. in diameter, the subulate or lance-subulate teeth 2.5-5.7 mm. long, the whole becoming membranous, ruptured, marcescent; petals commonly ochroleucous, more or less faintly veined or distally suffused with lurid purple, the keel-tip maculate, rarely purple throughout; banner recurved through ± 40°, oblanceolate or rhombic- oblanceolate, 22-26 mm. long, 7-10 mm. wide; wings 19-24 mm. long, the claws 10.5-12.5 mm., the narrowly lanceolate blades 8.5-13 mm. long, 2-2.4 mm. wide, slightly incurved at or beyond the middle; keel 18-22 mm. long, the claws 11-14 mm., the lunately oblanceolate blades 7.5-9.5 mm. long, 2.7-3.2 mm. wide, gently incurved through 70-90° to the broadly rounded’ apex; anthers 0.55-0.7 mm. long; pod ascending (humistrate), readily deciduous, obliquely lance-ovoid, 1.5—3 (4) cm. long, (5) 6—9 mm. in diameter, obcompressed toward the obtuse base, strongly incurved and contracted distally into a triangular- or deltoid-acuminate, firmly cuspidate beak, both the sutures prominent, the fleshy, green valves becoming brown, firmly leathery or subligneous, rugulose-reticulate, villous-hirsute with widely spreading, lustrous hairs up to 3 mm. long rarely mixed with shorter curly ones, the vesture not or scarcely concealing the surface of the valves, becoming tawny when dry; dehiscence apical, after falling; ovules 26—36; seeds not seen.—Collections: 18 (i); representative: Jones 1690 (NY, POM); Jones (from Johnson’s Pass) in 1890 (POM), and (from Cedar Fort) in 1896 (POM); Tidestrom 2083 (NY); Ripley & Barneby 4778 (CAS, RSA).

    Gravelly clay benches and hillsides on limestone or sandstone, often in light shade of juniper or piñon, 4500—6500 feet, locally plentiful in scattered stations in the drier mountains around the east edge of the Great Basin in Utah, from the south shore of Great Salt Lake south around both sides of Utah Lake to the middle Sevier Valley and, apparently becoming rarer, to the east edge of the Escalante Desert in Iron County.—Map No. 84.—April to June.

    Astragalus eurekensis (of Eureka, Utah) Jones, Contrib. West. Bot. 8: 12. 1898 ("Eurekensis"), based on A. glareosus sensu Jones in Zoë 3: 291. 1892 (non Dougl.).—"...occurs sparingly throughout the Great Basin region of Utah...’’—Lectotypus (Rydberg, 1925, p. 234; Barneby, 1947, p. 482), collected at Eureka, Juab County, Utah, by M. E. Jones in 1891, POM! isotypus, GH! cotypi (fr.), collected by Jones the same year at Homansville, Juab County, GH, POM!—Xylophacos eurekensis (Jones) Rydb. Fl. Rocky Mts. 1063. 1917.

    Astragalus Newberryi × eurekensis Jones, Rev. Astrag. 217. 1923.—"Lake Point Utah, No. 1743, May 29, 1880."—Holotypus (Jones 1743), POM! isotypi, NY (3 sheets), US!—Xylophacos medius (intermediate, supposedly, between A. Newberryi and A. eurekensis) Rydb. in Bull. Torr. Club 52: 232. 1925.

    The Eureka milk-vetch is closely related to A. Newberryi, and although they are almost always easily recognized alive or dead by trivial or imponderable characters of vesture and coloring, substantial and constant differential criteria are lacking. Flowering plants of A. eurekensis are usually identified by the more closely appressed vesture of the petioles and scapes and the whitish (when dry stramineous) petals more or less suffused distally or also lined with lurid purple, combined with foliage of a dull leaden-gray. Its simply hirsute rather than hirsute and tomentose pod is ordinarily distinctive. However I have seen a few examples of scapes hirsute for at least a short distance below the flowers, and of a pod bearing some short curly hairs intermixed with the lustrous longer ones. The typus of Xylophacos medius had apparently purple (according to Jones only purple-tipped) flowers, suggestive of A. Newberryi, and is further remarkable for its few (mostly 5 or 7), rather large leaflets. There is evidence that whitish flowers characteristic of A. eurekensis can occur on plants with leaflets as large and few, and the purple coloring of A. medius is therefore reasonably interpreted as a minor individual variation. There is no particular reason to interpret Ar. medius as a hybrid involving A. eurekensis and A. Newberryi, especially since the second supposed parent has not been traced north nearly so far in Utah.

    The history of A. eurekensis goes back to 1877, when Edward Palmer first discovered it near the southern limit of its range, at Paragonah, in Iron County. The collection was referred by Gray (in herb.) to A. Newberryi, a species of which the densely woolly pod was yet unknown. In the early nineties Jones began to find the species abundant in the mountains west and south of Salt Lake City, and identified it first with A. Chamaeleuce, later with the then misunderstood A. glareosus. The first description of A. eurekensis as an independent entity appeared under the latter name.