Astragalus preussii A.Gray var. preussii
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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
“Banks of the Rio Virgen a tributary of the Colorado in Nevada, near the eastern borders of California, ... Fremont, in second expedition, 1844..."-Holotypus, NY! isotypus (fragm.), GH!
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Synonyms
Tragacantha preussii (A.Gray) Kuntze, Phaca preussii (A.Gray) Rydb., Rydbergiella preussii (A.Gray) Rydb., Astragalus preussii var. latus M.E.Jones, Astragalus preussii var. arctus E.Sheld., Rydbergiella arcta (E.Sheld.) Rydb., Astragalus arctus (E.Sheld.) Tidestr., Jonesiella arcta (E.Sheld.) Rydb.
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Description
Variety Description - Leaflets extremely variable in size and number, generally (7) 11-15 and of broad outline west of the Grand Canyon, 13-23 in the Colorado Basin above the Canyon, in the latter area varying from orbicular to linear, either from the lower to the upper leaves of a single plant, or from plant to plant in a colony, or from colony to colony; banner 17.4—24 mm. long.
Distribution and Ecology - Alkaline clay flats, talus in canyons, gravelly or sandy washes, and along draws in gullied badlands, confined to selenium-bearing soils derived from sandstone or limestone, 1700-5150 feet, locally plentiful but rather scattered, Colorado Basin in southestem Utah and northern Arizona, west to southern Nevada and extreme east San Bernardino County, California.—Map. No. 72. Late March to May, the fruit long persistent.
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Discussion
The Preuss milk-vetch is a coarse, ill-scented but rather handsome astragalus, and perplexingly variable. In the type-region west of Grand Canyon, the populations are characterized by few (mostly 11-15) broadly obovate, obtuse or retuse leaflets (Clokey 8406, CAS, NY, UC, WIS, WS; 8460, CAS, NY, UC, WS; C. B. Wolf 10,533, CAS, RSA). In the Colorado Basin above the Canyon, the leaflets except in seedling plants (cf. Cutler 2283, CAS, NY, WIS) are almost consistently more numerous, commonly 17-25, and vary greatly in outline within a colony, sometimes from leaf to leaf on a single plant. In northern Coconino County, Arizona, the leaflets are mostly small, obovate, retuse or emarginate (Barneby 12,669, CAS, NY, RSA); in Emery and Grand Counties, Utah, the lower leaves are composed of oblong-elliptic, obtuse leaflets, but these vary upward along the stems into linear-elliptic, mucronulate or sharply acute ones up to 2.5 cm. in length (Holmgren & Hansen 3313, NY, UTC, WS, WTU; Ripley & Barneby 5400, CAS, RSA; Rydberg & Garrett 8436, 8481, 8482, NY; Jones from San Rafael Swell in 1914, NY, POM). The aspect of the whole plant changes with the type of leaflet, but the flower and pod remain essentially uniform. Experience with the living plants suggests that the populations in southeastern Utah are on the average taller and of more bushy growth-habit than those in Nevada, and the petals are generally of a more vivid purple. The curious spurs or branchlets inserted between petiole and peduncle at the upper axils are more frequent in the eastern area. Possibly var. latus should be revived for the variants in the Colorado Basin; for the present, however, it seems preferable to treat the leaf-variants as representing evolutionary trends too little advanced to deserve taxonomic notice.
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Objects
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Distribution
Utah United States of America North America| Arizona United States of America North America| Nevada United States of America North America| California United States of America North America|