Astragalus sheldonii (Rydb.) Barneby
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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
"Type collected in Horse Creek Canyon, Wallowa County, Oregon, May 14, 1897, Sheldon 8032 ... -Holotypus, NY! isotypi, MO, US!
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Synonyms
Tium sheldoni Rydb.
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Description
Species Description - Usually stout and rather coarse, with a thick, woody taproot and shortly forking suffruticulose caudex, strigose-pilosulous with fine, ascending and incumbent hairs up to 0.5-0.9 mm. long, the pale green or stramineous, striate stems thinly so, the herbage greenish or cinereous on the lower surface, the leaflets glabrous above; stems several, erect and ascending in clumps, simple above the immediate base, (3) 5-38 cm. long, composed of 3-7 developed internodes up to 2.5-12 cm. long, the whole commonly shorter, sometimes a little longer than the longest inflorescence; stipules 3-10 mm. long, the lowest adnate (sometimes through 4 mm.) to the petiole-base, papery-scarious or early becoming so, ovate or ovate- acuminate, amplexicaul-decurrent around half or a little more of the stem s circumference, the upper ones narrower, more shortly adnate, with lance-acuminate, mostly erect, subherbaceous blades, their margins commonly beset with a few minute processes; leaves 7-19 cm. long, the lowest long-petioled, the upper more shortly so, with (17) 23-35 (39) oblong-obovate, elhptic, or narrowly oblanceolate, retuse, obtuse, or sometimes subacute, flat leaflets 5—22 mm. long, peduncles stout, stiffly erect, (11) 16-30 cm. long; racemes loosely 10-30 (35)-flowered, the flowers nodding and at early anthesis retrorsely imbricated, the axis early elongating, (3) 6-16 cm. long in fruit; bracts submembranous, linear- or lance- acuminate, 2.5-9 mm. long; pedicels at anthesis arched outward, 1.3-2 mm. long, in fruit clavately thickened, erect, 2.5-6 mm. long; bracteoles 0-2; calyx 8.5-12.6 mm. long, thinly strigulose-pilosulous with black or mixed black and white hairs, the oblique disc 0.9-1.4 mm. deep, the membranous, pallid, deeply campanulate tube 5.6-7.5 mm. long, 3.5-4.S mm. in diameter, the subulate or linear-subulate teeth 2-5.2 (6) mm. long, either erect or arcuately spreading or recurved the whole becoming papery-scarious, ruptured but marcescent; petals white or creamy-white immaculate; banner gently recurved through about 45°, rhombic-oblanceolate or -obovate, shallowly notched. 15.5-21.5 mm. long. 7-11 mm. wide; wings 13.4-19 mm. long, the claws 6.2-9 mm. the nearly straight, obliquely oblong-oblanceolate, obtuse or emarginate blades 8-11.8 mm. long. 2.5-4.2 mm. wide; keel 11.5-14.4 mm. long. the claws 5.9-8 4 mm., the lunately half-elhptic blades 5.6-7.6 mm. long. (3.2) 3.7-4 mm. wide, gently or rather abruptly incurved through 75-85 (90°) to the sharply deltoid apex; anthers 0.7-0.9 mm. long, pod erect, sessile or elevated on an obscure, stout stipe up to 1.5 mm. long, the body narrowly oblong-ellipsoid, (1.5) 1.7-2.3 cm. long, (4) 4.5-6.3 mm. in diameter, straight or a trifle incurved, abruptly obtuse or truncate at base, contracted distally into a triangular-acuminate, sharply cuspidate, laterally compressed beak, otherwise obcompressed, keeled ventrally by the prominent thick ventral suture, openly grooved dorsally, the green, fleshy, at length leathery and stramineous transversely rugulose-reticulate valves either minutely strigulose with black complete septum 1-1.6 mm. wide; ovules (20) 24-31; seeds brown, smooth but dull, 2.3-2.6 mm. long.
Distribution and Ecology - Stony meadows, bunchgrass prairies, or rocky hillsides among low sagebrush in deep, dry soils derived from basalt, 1750-3500 (4200) feet, locally plentiful in the hill country about the lower Salmon and adjoining Snake Rivers in Idaho, Lewis and Nez Perce Counties, Idaho, Asotin County, Washington, and along creeks running to the Snake on the northeastern slope of the Wallowa Mountains, Wallowa County, Oregon.—Map. No. 63.—May to July, the fruit long persisting.
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Discussion
The Sheldon milk-vetch is closely related to A. reventus, differing consistently only in its narrower, more nearly bilocular pod; but its specific status is reinforced by different modes of variation in many organs (especially the common presence of a short stipe and shorter calyx-tube) and by its vicariant range of dispersal. Whereas A. conjunctus is confined to the granitic formations of the Blue Mountains, the present species is as rigidly restricted to basalt soils. The majority of the populations of A. Sheldoni are distinguished further by their pubescent ovary and pod strigulose with either white or black hairs, but a glabrous-fruiting form is known from a small area near the mouth of the Grande Ronde in Asotin County, Washington (cf. Sheldon 8236, NY, UC; Head 671, 681, RSA), while both phases occur close together on the opposite side of the Snake River in Nez Perce County, Idaho (cf. Christ 14,204, NY; W. H. Baker 8921, ID, RSA). In the valley of the Clearwater A. Sheldoni is sometimes associated with A. collinus, and the two species, alike in their dense racemes of nodding, retrorsely imbricated flowers, have now and then been needlessly confused. The basally pouched calyx and shortened, sigmoidally arched banner of A. collinus are amply distinctive even without the beginnings of the pendulous, long-stipitate, unilocular fruit. The Sheldon milk-vetch was first collected in 1884, in Nez Perce County, Idaho, by J. B. Leibere (ORE).
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Objects
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Distribution
Washington United States of America North America| Idaho United States of America North America| Oregon United States of America North America|