Astragalus atratus var. owyheensis (A.Nelson & J.F.Macbr.) 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
Astragalus atratus var. owyheensis (A.Nelson & J.F.Macbr.) M.E.Jones
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Type
"No. 1887, collected July 2, 1912, above the Hot Hole of the East Bruneau, Owyhee Co., Idaho, is the type." Holotypus, RM! isotypi, GH, ID, MO, NY, POM, US!
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Synonyms
Astragalus owyheensis A.Nelson & J.F.Macbr., Tium owyheense (A.Nelson & J.F.Macbr.) Rydb.
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Description
Variety Description - Essentially like var. atratus but extremely slender and delicate in all its parts, the herbage greenish-cinereous, the leaflets glabrous or nearly so above; steins mostly short, 1-15 (20) cm. long, numerous and closely tufted, greatly surpassed by the inflorescences; stipules 1-3.5 mm. long; leaves (2) 4-14 cm. long, with 7-11 (13) remote, often scattered, linear-elliptic, involute or conduplicate leaflets 1.5—7 (10) mm. long, those of the upper leaves reduced in size, the terminal one continuous with the very slender or filiform rachis; peduncles subfiliform, (1.5) 3.5-12.5 cm. long; racemes remotely (3) 5-12-flowered, the axis (2) 5-17 cm. long in fruit; calyx 3-5.8 mm. long, the tube 2.3-4 mm. long, 1.7-2.7 mm. in diameter, the teeth 0.7-2.1 mm. long; petals whitish, faintly lavender-tinged; banner 6.3-9.9 mm. long, 4-6.4 mm. wide; wings 0.8-1.9 mm. longer, 7.4-10.5 mm. long, the claws 2.8-4 mm., the obliquely obovate or half-obovate blades 5.2-7.2 mm. long, 2.2—3.6 mm. wide just below the rounded, erose, or shallowly emarginate apex; keel 5.9-7.7 mm. long, the claws 2.9-4 mm., the blades 3.5-4.2 mm. long, 1.9-2.4 mm. wide; pod stipitate, the stipe 1-2 mm. long, the body narrowly elliptic-oblanceolate in profile, 1.4—2 cm. long, 3—4 mm. in diameter, the thinly paper valves not inflexed; ovules 10-17.
Distribution and Ecology - Dry hillsides and gravelly flats, on basalt, usually taking shelter under and entangled in low sagebrush, 3500-6000 feet, local but plentiful in scattered stations, from the headwaters of the Powder and Burnt Rivers in Baker and northern Malheur Counties, Oregon, to adjoining Washington County, Idaho; also along the Bruneau River in Owyhee County, Idaho, south and east to southern Twin Falls County and the headwaters of the Humboldt River in northern Elko County, Nevada.—Map No. 54.—May to July.
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Discussion
The Owyhee milk-vetch is one of the most delicately fashioned of all astragali. Its many very slender stems, its threadlike peduncles and petioles (the latter beset with tiny, scattered leaflets), and its airy, remotely flowered racemes of small, whitish flowers succeeded by narrowly ellipsoid pods pendulous from capillary pedicels all contribute to a characteristic elegance of habit. It has been mentioned above that around the sources of the Humboldt River in Elko County, Nevada, there occur forms of var. atratus nearly as slender, and in this area the two varieties can be told apart only by examining the shape of the wing-tips or the development of septum in the pod. According to Jones (1923, l.c.) the plants of var. owyheensis can become three feet in diameter in grassy meadows; in the more usual habitat of stony flats and dry hillsides among sagebrush, the loosely woven mats or semiprostrate tufts are rarely half as large. The peduncles and racemes together are commonly longer than the proper stems.
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Objects
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Distribution
Oregon United States of America North America| Idaho United States of America North America| Nevada United States of America North America|