Astragalus inyoensis E.Sheld.
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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. . .No. 791, Death Valley Expedition; collected May 20, 1891, on the Darwin Mesa, near Mill Creek Divide, Inyo County, California, by Frederick V. Coville." Holotypus, US! isotypi, BM, MINN!
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Synonyms
Tium inyoense (E.Sheld.) Rydb.
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Description
Species Description - Slender, diffuse, sparsely leafy, strigulose nearly throughout with straight, appressed or subappressed hairs up to 0.35-0.55 mm. long, the stems thinly so, the herbage cinereous, but the leaflets glabrous above, densely ciliate; stems several or numerous, radiating from the root-crown, prostrate with ascending tips, (1) 1.5-4.5 (6) dm. long, simple or divaricately branched or spurred at 1-3 nodes preceding the first peduncle, zigzag distally in age; stipules 1.5-4.5 mm. long, ovate- triangular or broadly lanceolate, the lowest early becoming papery-membranous, the median and upper ones herbaceous, commonly deflexed, all ± semiamplexicaul; leaves divaricately spreading, 1.5—4.5 cm. long, mostly shorter than the internodes, the lowest shortly petioled, the rest subsessile, with (9) 11—19 (21) usually crowded, obovate, oblanceolate, or oblong-obovate, obtuse or retuse, conduplicate and backwardly curved leaflets (2) 3—10 mm. long; peduncles divaricately spreading-incurved, 2.5—7 cm. long, as long or longer than the leaf; racemes loosely 6-15- flowered, the axis (1.5) 2.5—7 cm. long in fruit; bracts submembranous, ovate- triangular, 0.8—1.5 mm. long; pedicels at first ascending, 0.8—2 mm. long, in fruit arched out- and downward, little thickened, 1—2.5 mm. long; bracteoles 0—2, minute when present; calyx 3.7—5.8 mm. long, strigulose with white or mixed black and white hairs, the subsymmetric disc 0.7-1.1 mm. deep, the campanulate or somewhat vase-shaped, purplish tube 2.4—3.7 mm. long, 2—2.6 mm. in diameter, the subulate teeth 1.1-2.4 mm. long, the whole becoming papery, marcescent unruptured; petals pink-purple, the banner striate with purple veins; banner obovate- cuneate or rhombic-suborbicular, openly notched, 8.6—10.8 mm. long, 5.6—9. mm, wide; wings 1.1-93 mm. long, the claws 2.7-3.3 mm, the oblong-oblanceolate, obtuse, subtruncate, or obscurely emarginate, nearly straight blades 5.5-7 mm. long, 2.2-3.3 mm. wide; keel ± equaling the wings (0.5 mm. shorter to 0.6 mm. longer), 8.2-9.6 mm. long, the claws 3.4-4 mm, the broadly triangular to half-obovate blades 5-6.2 mm. long, (2.8) 3-3.7 mm. wide, incurved through 85-90 to the broad, blunt apex; anthers 0.45-0.65 mm. long, pod declined, stipitate, the stout, straight stipe 2-5 mm. long, the body obliquely ovoid-acuminate, 1.2 1.6 cm. long, 3.6-5 mm. in diameter, gently to very abruptly and strongly incurved through 1/8-1/2-circle, obcompressed-triquetrous just above the cuneate base, contracted distally into a triangular-acuminate, laterally compressed beak terminating in an erect, rigid, subulate cusp 3—4 mm. long, carinate ventrally by the prominent suture, deeply sulcate dorsally, the somewhat fleshy, purplish, strigulose valves becoming stiffly leathery and coarsely cross-reticulate, the septum incomplete, 0.6-1 mm. wide; seeds ochraceous, purple-speckled, pitted but somewhat lustrous, 2.1-2.8 mm. long.
Distribution and Ecology - Gravelly banks, rocky streambeds, and open sandy or clay flats among sagebrush and nut pines, mostly on volcanic (perhaps sometimes calcareous) bedrock, 5000-7800 feet, locally plentiful in the desert mountains bordering Owens Valley to the east in Inyo County, California, from near Westgaard Pass southward through the Inyo Mountains to Darwin Mesa.—Map No. 50.—May to July.
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Discussion
The Inyo milk-vetch was discovered by Coville at the same time and in the same place as A. atratus var. mensanus, and these two rare astragali, both endemic to Inyo County, still occur in close association on the divide between Saline and Panamint Valleys. A. inyoensis prefers gravelly or sandy spots bare of ground cover, where the prostrate zigzag stems, radiating in all directions from the root-crown, form symmetrical, loosely woven mats of foliage; var. mensanus struggles up out of the shelter of low bushes and consequently has a weak, untidy appearance. The two species, which are similar in many technical features, are easily told apart by the differently shaped flowers and different curvature of the pods.
More than half the known collections of A. inyoensis originated in Westgaard Pass (or Cedar Flat) where a dip in the mountain crest serves as a line demarcating the White Mountains from the Inyo Range to the south. The type station lies at its southern limit of dispersal about sixty miles distant, and one intermediate locality, on the slopes of Waucoba Peak, is on record. Probably all the material examined, which is extremely uniform in detail, was derived from three major populations.
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Objects
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Distribution
California United States of America North America|