Astragalus adsurgens var. tananaicus (Hultén) Barneby
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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
"Alaska Range distr.: Alaska Highway, mile 1247, Anderson 9188 (Hb Hulten); Rapids Lodge, Anderson 2204 (Hb Hulten, type...)." Typus not examined, but the photo-typus (Hult., l.c., fig. 1) and a topotypus, Scamman 4623, GH, are decisive.`
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Synonyms
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Astragalus tananaicus Hultén, , Astragalus adsurgens subsp. viciifolius S.L.Welsh
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Description
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Variety Description - Habit of the species, but usually low, the stems (3) 7-27 cm. long, composed usually of ± 2-5, rarely more numerous internodes; leaves (2) 4-10 cm. long, with (7) 11-17 leaflets (0.4) 0.7-2.5 cm. long; peduncles 4-12 cm. long; racemes 10-20-flowered, the axis 1-3.5 cm. long in fruit; calyx 5.6-6.8 mm. long, strigulose with black or mixed black and white hairs, the tube 4.6-5.7 mm. long, 3-3.8 mm. in diameter, the teeth 0.4-1 (2.1) mm. long; petals white (with lavender-purple keel-tip), or whitish tinged with slate-blue, or lavender drying bluish; banner 11.5-16.2 mm. long, 4.5-6.6 mm. wide; wings 9.7-13.8 mm. long, the claws 5-6.5 mm., the linear-oblong or -elliptic blades 5.2-8 mm. long, 1.7-2.8 mm. wide; keel 8.7-12.2 mm. long, the claws 5.7-6.7 mm., the blades 4.5-6 mm. long, 2.2-3 mm. wide; pod stipitate, the stipe 0.7-1.8 mm. long, the body narrowly oblong or oblong-elliptic in profile, 6-12 mm. long, 2.5-4 mm. in diameter, densely strigulose with short black and longer, straighter, ascending, white hairs; ovules (9) 12-16 (18).
Distribution and Ecology - Shaley river bluffs, shingle bars, and pebbly banks of streams, in disturbed gravelly soil along highways and about airfields, or in dry grassy meadows and hillsides, common locally, 400-2500 feet, apparently confined to the Yukon River drainage in southern Yukon and eastcentral Alaska.—Map No. 77.—June to early August.
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Discussion
The Tanana milk-vetch was compared in the protologue with A. agrestis and with A. brevidens Rydb., and its pod was said not to be divided into two chambers. However it has all characteristics of importance in common with A. adsurgens, including the bilocular pod of sect. Onobrychoidei, and it is closely akin to the American A. adsurgens var. robustior. Flowering specimens of var. tananaicus can generally be separated from var. robustior by the short calyx-teeth, but this character sometimes fails (cf. Viereck 1779, COLO). During the preliminary studies of this group, I became satisfied that Hulten’s species represented no more than a disjunct geographic race of var. robustior, one that presumably survived the Tertiary glaciations in an Alaskan refugium and had acquired with the passage of time a certain individuality of facies. At the suggestion of J. M. Calder, whose field knowledge of Astragalus in Yukon and British Columbia is unrivaled, I went over the material once again, discovering the short but definite stipe in the few fruiting collections available. A stipe of the same sort is known to occur in some Asiatic specimens of what I take to be characteristic var. adsurgens, so that the character may not be entirely stable. For the present, however, the stipe in conjunction with almost always abbreviated calyx-teeth provides a basis for distinguishing the presumably relic Alaskan var. tananaicus from the Cordilleran var. robustior. Since the disappearance of the ice sheets, the latter must have advanced northward along the Rocky Mountain piedmont to reach its northern known natural limit on the Liard River; and in recent years it has moved on as an introduction into the Yukon Valley, where it was collected along the Dawson-Whitehorse highway at 62° 50' N. (Calder & Gillett 25,837, NY).
The var. tananaicus is itself composed of two minor races. The strictly typical one, found in McKinley Park and along the Tanana River upstream from Fairbanks, has greenish leaves, a slightly tumid calyx, and whitish petals with lilac keel-tip. In the upper Yukon Valley the foliage is commonly cinereous, the calyx narrower, and the petals all pinkish-lavender drying bluish. Except for the short calyx-teeth, plants of the latter type closely resemble low prairie forms of var. robustior.
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Objects
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Distribution
Yukon Canada North America| Alaska United States of America North America|