Astragalus toanus M.E.Jones
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Authors
Rupert C. Barneby
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Authority
Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(1): 1-596.
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Family
Fabaceae
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Scientific Name
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Type
“... on the slopes of the Toano Range, Eastern Nevada, in open ground . . . out of flower July 21, 1891. Lectotypus, a fruiting plant labeled "Ferguson Spring, Nevada, near Deep Creek," POM! isotypus, labeled "Toano Range," US! probable isotypi, dated Jul
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Synonyms
Cnemidophacos toanus (M.E.Jones) Rydb., Astragalus campylophyllus Greene
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Description
Species Description - Commonly robust, sparsely leafy and junceous, with a thick, woody, multi- cipital taproot and knotty crown or shortly forking caudex just below soil-level, strigulose nearly throughout with flattened, appressed and subappressed hairs up to 0.2-0.6 mm. long, the young shoots commonly cinereous, the stems and herbage greenish or thinly cinereous at maturity, occasionally green and nearly glabrous, the leaflets either glabrous or pubescent above; stems numerous, erect and ascending in bushy clumps, (1.5) 2.5-5 dm. long, leafless at base, simple or paniculately branched at and below the middle; stipules 1.5—6.5 mm. long, dimorphic, the lowest amplexicaul and connate into a papery-scarious, truncate or obtusely bidentate sheath (sometimes ruptured by the enlarging stem), the upper ones smaller, herbaceous, ovate or deltoid-acuminate, about semiamplexicaul, free; leaves 2.5—10 cm. long, with stiff, channelled petiole and rachis, the lower ones bearing 1—4 (6) pairs of distant, irregularly inserted, linear-filiform or rarely linear-oblong, obtuse or subacute, involute leaflets 3-30 mm. long decurrent into the rachis, the terminal one appearing as a linear, often falcately recurved prolongation of the rachis longer than the last lateral pair, or all leaves, and nearly always the uppermost, reduced to a linear phyllode devoid of leaflets; peduncles stout, strict, 6-25 cm. long; racemes loosely 7-35-flowered, the flowers ascending, the axis (1.5) 3-30 cm. long in fruit; bracts herbaceous becoming papery, ovate or lanceolate, 1-2 (3) mm. long; pedicels ascending, straight, at anthesis 0.8-2 mm., in fruit greatly thickened, 2-3.5 mm. long; bracteoles 0-2, minute when present; calyx 4.6-7.3 mm. long, densely strigulose with white, black and white, or rarely almost all black hairs, the oblique disc (0.6) 0.9-1.5 mm. deep, the campanulate or subcylindric, ventrally convex tube 4.1-6.1 mm. long, (2.6) 3-3.9 mm. in diameter, the deltoid or lanceolate teeth 0.5-2 mm. long, the ventral pair often shortest and broadest, the whole becoming scarious, ruptured, marcescent; petals bright pink-purple, the wing-tips paler or white; banner recurved through 40-45°, rhombic-ovate, or with long-cuneate claw abruptly expanded into an oval-ovate blade, (13) 15-20 mm. long, 7.8-10 mm. wide; wings (11.6) 13.517 mm. long, the claws (4.2) 5.2-7 mm., the narrowly lance-oblong or oblanceolate, obtuse or subemarginate, nearly straight blades (7.9) 8.6-11 mm. long, 1.52.9 mm. wide; keel (9.5) 10.5-13.5 mm. long, the claws (4.3) 5.2-7 mm., the half-obovate or lunately half-elliptic blades 5.2-7.2 mm. long, 2.5-3.1 mm. wide, incurved through 50-80 (90)° to the rounded, sometimes obscurely porrect apex; anthers 0.55-0.7 mm. long; pod erect or exceptionally spreading and ascending, sessile, elliptic, narrowly oblong, or oblong-elliptic in profile, straight or a trifle incurved, (1) 1.3-2.5 cm. long, 3.7-5.5 (7) mm. in diameter, obtuse at base, cuneately or subtruncately contracted distally, stiffly cuspidate at apex, a trifle laterally compressed, bicarinate by the salient, thick and cordlike sutures, the faces convex, the fleshy, green or sometimes purple-speckled, lustrous valves becoming stramineous, leathery or subligneous, rugulose-reticulate, varying from glabrous to minutely puberulent or sometimes densely strigulose-cinereous, not inflexed; ovules (14) 16-26; seeds smooth, brown, 2.9-3.8 mm. long.
Distribution and Ecology - Barren, calcareous clay banks, sandy shale or clay bluffs and knolls, sometimes on gumbo-clay flats with A triplex and Sarcobatus, 2500-5900 feet, of scattered occurrence but forming extensive colonies where selenium-rich soils are available, plentiful in eastcentral and northeastern Nevada, especially in the upper Humboldt Valley, and extending just east into northwestern Utah; again plentiful along the Snake and lower Bruneau Rivers in Idaho, and extending just into Malheur County, Oregon; occasionally westward in Nevada to the Humboldt Sink, the Quinn River, and the lower Walker River in Lyon County, and south to the sink of the White River in northeastern Nye County.—Map No. 49.—May to July.
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Discussion
The Toano milk-vetch is the prototype of a group of Pectinati adapted to desert or semidesert conditions and distinguished by greatly modified foliage and so-called junceous or ephedroid habit of growth. In this and the three species next in order the leaves are composed of few, small, irregularly inserted leaflets; and some of them, either high on the stems or nearly throughout the plant, are reduced to a slender, tapering rachis which resembles a branchlet except for the channeled upper side. They differ further from the Pectinati described up to this point (but see a possible exception in A. linifolius) in their pink-purple and not white or ochroleucous flowers. The modification of the foliage is of the sort achieved also by several Lonchocarpi, Genistoidei, and Hookeriani of the intermountain states; but all of the latter have papery pods and most of them a much more shallowly campanulate calyx. Of its immediate group, A. toanus is the commonest and most widely dispersed, but is absent from the Colorado and Uinta Basins to which its three close relatives are endemic.
The typical form of A. toanus, as seen about the sources of the Humbolt in northeastern Nevada, has relatively large flowers and consistently glabrous fruits. Along the Snake River in Idaho, the petals and calyx are ordinarily a little smaller, and the pod is commonly pubescent, at least sparsely so and often strigulose-cinereous. However in Gooding County, between Bliss and King Hill, there is an enclave of glabrous-fruiting populations which cannot be effectively separated from the Nevadan form. Furthermore, the type-collection of A. campylophyllus, from Humboldt County, Nevada, consists of three sheets and includes plants with glabrous and others with cinereously pubescent fruits. Very likely the two sorts in this collection are samples of different populations, but even so the two forms must occur close together in the Humboldt Desert. There seems no rational basis for segregating either a small-flowered or a pubescent-fruiting phase.
When past flowering, the Toano milk-vetch forms broomlike, apparently leafless tufts of stiffly fastigiate outline, identifiable into late summer by the pods which remain long on the desiccating stems, their valves bent outward in a widely gaping dehiscence and soon emptied of their seeds. Because of the sparseness of the foliage and the freedom with which the loose spikes of comparatively large, richly colored flowers are produced after a rainy spring, a flourishing colony of A. toanus provides a spectacle of color hardly matched in its bleak habitat of barren knolls rising out of the sagebrush desert.
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Objects
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Distribution
Nevada United States of America North America| Utah United States of America North America| Idaho United States of America North America| Oregon United States of America North America|