Astragalus iodanthus S.Watson var. iodanthus
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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(2): 597-1188.
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Family
Fabaceae
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Scientific Name
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Type
"Collected by Dr. Bloomer and Dr. Torrey near Virginia City, and not rare in the foothills of Western Nevada from the Virginia to the West Humboldt Mountains; 4500-6000 feet altitude... 269."—Lectotypus, collected by Sereno Watson at 5000 ft. in the West
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Synonyms
Astragalus iodanthus var. diaphanoides Barneby
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Description
Variety Description - Usually thinly pubescent, the stems stramineous or pale green and nearly glabrous; leaflets (7) 11-19 (21), sometimes conspicuously white-ciliate; calyx (5) 5.5-8 mm. long, the disc 0.7-1.4 mm. deep, the tube (3.4) 3.7-5 mm. long, 2.1-2.7 mm. in diameter, the teeth (1.3) 1.5-3 mm. long; petals brilliant wine- purple (drying violet), lilac, or whitish with purple keel-tip, exceptionally cream- colored and concolorous; banner (10) 12—15.5 mm. long; wings 1—2.4 mm. shorter, the claws 4—6.3 mm., the blades (5.2) 6—8 mm. long, 1.7—2.3 mm. wide; keel 1—4.6 mm. shorter than the banner, 7.8—12 mm. long, the claws 4—6.1 mm., the blades 4.1-7.3 mm. long, 2.1-2.6 mm. wide; pod (2) 2.5-4 cm. long, (4.5) 5—8.5 mm in diameter, variable in compression but most commonly more dorsiventrally than triquetrously flattened; ovules 18—30.
Distribution and Ecology - Dry hillsides and valley floors, in loamy, sandy, or gravelly clay soils mostly on volcanic bedrock, nearly always among sagebrush, common and locally plentiful between 5000 and 7800 feet throughout the valley of the Humboldt River and its tributaries across the width of northern Nevada (south along the Reese River to northern Nye County), extending just into southeastern Oregon, northwestern Utah (western Tooele County), and the plains and Sierra foothills of eastern Lassen and Sierra Counties, California, and south through the hill-country of westcentral Nevada to the east slope of the Sierra Nevada in Mono County, California; about the Humboldt and Carson sinks descending to barren, alkaline clay or sandy slopes and washes as low as 4000 feet, there associated with Artemisia spinescens and Atriplex.—Map No. 133.—April to early July.
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Discussion
The typical form of the Humboldt River milk-vetch, var. iodanthus, is very variable in vesture, in proportionate length and coloring of the petals, and in length and curvature of the legume. The various types of fruit, at first sight so remarkably disparate, represent individual variants of sporadic occurrence, but variation in other characters is, at least to some small degree, correlated with elevation and environment. The common form of var. iodanthus in the mountains, in protected spots in the sagebrush valleys, and elsewhere where the soil is rich or the exposure cool, is nearly glabrous up to the black-strigulose inflorescence and has relatively long, well-graduated petals of a bright claret-purple which turns violet on drying (but tends to fade after a year or two in the herbarium). In the low deserts of northwestern Nevada and in adjoining California, the prevailing form tends to be more densely strigulose, especially about the margins and midribs of the leaflets, and the petals, which vary from pale lilac to whitish or cream-colored, with keel tip either maculate or concolorous, are much less strongly graduated so that the keel appears large and prominent. A plant of the latter sort furnished the typus of var. diaphanoides, which is probably best interpreted as an ecotype without claims to taxonomic recognition. Both phases of the species are known to occur near the type-locality in the West Humboldt Mountains, Watson’s original "violet-flowered" phase (with brightly mottled pod) in the juniper-sagebrush association between 5600 and 6300 feet, and possibly higher on Star Peak, the lowland phase with pale flowers and faintly mottled or green pods in the foothill canyons at about 4700 feet. When var. diaphanoides was described, it was noted that the valves of the pod, in contradistinction to those of typical var. iodanthus as there conceived, are often inflexed through the lower half or more as a narrow but evident septum, but a similar and sometimes even wider septum has since been found on the same plants with a long, bright purple flower. The complete disappearance of the septum, especially from near the base of the pod where it is most easily overlooked, is rare in the species as a whole.
Another variant, remarkable in its way, has been collected in the Trinity Mountains, Pershing County, Nevada (Ripley & Barneby 5637, CAS, RSA); the vesture in these plants is composed of loosely ascending incumbent or curly hairs, suggesting a passage toward A. pseudiodanthus, which differs further, however, in its subterranean root-crown.
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Objects
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Distribution
Nevada United States of America North America| Oregon United States of America North America| Utah United States of America North America| California United States of America North America|