Astragalus grayi Parry
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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 gravelly ridges bordering Owl Creek valley."—Holotypus, Parry 75a, collected on the Northwest Wyoming Expedition in 1873 at Owl Creek, Washakie County, Wyoming, GH! isotypi, G, K, NY, P, PH!
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Synonyms
Tragacantha grayi (Parry ex S.Watson) Kuntze, Ctenophyllum grayi (Parry ex S.Watson) Rydb., Cnemidophacos grayi (Parry) Rydb.
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Description
Species Description - Usually robust and in the context of the section relatively leafy, with a thick, heavy taproot and shortly forking caudex at or just below soil-level, thinly strigulose throughout or nearly so with fine, sometimes flattened, appressed and narrowly ascending hairs up to 0.2-0.6 mm. long, the stems and leathery herbage dark yellowish-green, the leaflets glabrous or less often strigulose above; stems several or numerous, erect and ascending in clumps, (1.5) 2—3.5 dm. long, simple, or strictly branching at or below the middle; stipules firm, 2.5—10 mm. long, dimorphic, those at the leafless lower nodes amplexicaul and connate into a papery, bidentate sheath sometimes ruptured by the stem’s expansion, the upper ones becoming more nearly herbaceous and progressively less connate upward, the uppermost deltoid- acuminate or caudate, free to the base or nearly so, the blades mostly squarrose, leaves (2.5) 4-10 cm. long, the upper ones subsessile, with stiff, grooved rachis and (1) 2—5 pairs of linear-oblong or oblanceolate, obtuse or subacute, conspicuously veined, flat but marginally elevated leaflets 1.5—5 (or in some early leaves only 0.6-1.5) cm. long, all or mostly contracted at base into a short, pallid pseu- dopetiolule but not jointed, the terminal one similar to but often longer than the last pair, tapering into and continuous with the rachis; peduncles erect, strict, 3—10 cm. long; racemes (5) 9—27-flowered, rather dense, the flowers ascending, the axis little elongating, (1) 1.5—7 cm. long in fruit; bracts firm, lanceolate, 2—7 mm. long, pedicels ascending, straight, at anthesis 0.7—2 mm., in fruit a little thickened, 1-3.5 mm. long; bracteoles commonly 2; calyx 6.5-10.3 mm, long, thinly to quite densely strigulose with white, rarely some or all black hairs, the slightly oblique disc 1-1.8 (2) mm. deep, the deeply campanulate to subcylindric tube 5.2-8 mm. long, 2.9-4.2 mm. in diameter, the lance-subulate teeth 1.2-2.5 mm. long, the ventral pair sometimes shorter, deltoid, the whole becoming scarious, investing the lower half of the pod; petals cream-colored, usually marcescent; banner recurved through ± 40°, (14.5) 15-22.5 mm. long, roughly rhombic in outline, the long- cuneate claw expanded upward into an ovate, emarginate blade (6.2) 7-12 mm. wide; wings (14.4) 15-19.2 mm. long, the claws 7-8.7 mm., the oblong-oblanceolate, obtuse, nearly straight blades 8.2-12 mm. long, 2.2-3.2 mm. wide; keel (11.5) 12.7-15.2 mm. long, the claws (6.3) 7.3-8.7 mm., the half-obovate blades 5.8-7.3 mm. long, 2.7-3.2 mm. wide; anthers 0.7-0.85 mm. long; pod erect or ascending at a narrow angle, sessile, narrowly oblong or oblong-elliptic in profile, straight or nearly so, 9-18 mm. long, 2.7-3.5 mm. in diameter, obtuse at base, abruptly contracted and cuspidate at apex, terete or a trifle laterally compressed, carinate by the thickened, salient, cordlike ventral suture, the green, fleshy, glabrous or rarely strigulose valves becoming stiffly leathery, brownish-stramineous, coarsely reticulate, not inflexed; ovules (14) 16-21 (23); seeds olivaceous, minutely pitted, dull, 3-3.5 mm. long.
Distribution and Ecology - Forming extensive colonies on adobe plains, on ridges of gullied clay hills and badlands, or in sandy pockets about shale and sandstone outcrops, 3850-7000 feet, locally plentiful on the upper forks of the Big Horn, Powder, and North Platte Rivers, from southeastern Carbon County, Montana, southeast to the Medicine Bow River in Carbon County, Wyoming.—Map No. 49.—May to July, the fruit long persisting.
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Discussion
Gray’s milk-vetch combines the foliage and whitish (though smaller) flower of A. Nelsonianus with the erect stems and erect pods of A. toanus; it thus connects the pale-flowered, more foliose Pectinati of the east continental slope with the largely purple-flowered, ephedroid species of the intermountain deserts. The flower of A. Grayi varies considerably in size, the variation being apparently sporadic and not correlated with a recognizable pattern of dispersal. The petals of A. Grayi are no more firmly attached to the rim of the floral disc than those of related species, but they persist about the forming pod, fastened there by the tightly investing calyx which does not fall away by circumscissile fission. As a consequence, the fruiting raceme has a characteristically untidy appearance. Rydberg (1929, 1. c.) described the pod as 4-5 mm. in diameter, but I have seen none so plumply oblong. The concept of Cnemidophacos Grayi as described in North American Flora was based partly on material of A. Nelsonianus; this may account for the discrepancy. Gray’s milk-vetch is reportedly tetraploid, with 2n = 44.
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Objects
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Distribution
Montana United States of America North America| Wyoming United States of America North America|