Astragalus bisulcatus (Hook.) A.Gray var. bisulcatus
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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
"Plains of the Saskatchewan, Drummond."—Holotypus, K! isotypus, GH!
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Synonyms
Phaca bisulcata Hook., Tragacantha bisulcata (Hook.) Kuntze, Diholcos bisulcatus Rydb., Astragalus haydenianus var. major M.E.Jones, Astragalus scobinatulus E.Sheld., Diholcos scobinatulus Rydb., Astragalus bisulcatus f. hedysaroides Gand., Astragalus haydenianus f. leiocarpus Gand., Astragalus haydenianus f. nelsonii Gand., Astragalus bisulcatus f. decalvans Gand., Diholcos micranthus Rydb., Astragalus diholcos Tidestr., Astragalus haydenioides Porter
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Description
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Variety Description - Usually stout and thinly pubescent, the stems sometimes glabrous; leaflets (11) 15-29, (0.5) 1-2.5 (3.2) cm. long; racemes 25-75-flowered, the axis 5-18 cm. long on fruit; bracts (2) 2.5-7 mm. long; calyx either pallid or red-purple, the tube 3.3-5.7 mm. long, 2.4-4 mm. in diameter, the subulate or subulate- setaceous teeth mostly 1.5-4.5 (6) mm., rarely only 0.7-1.3 mm. long; petals rose-purple, pallid but ± tipped or suffused with purple or lilac, or (as commonly) whitish with maculate keel-tip, rarely pure white; banner (10) 10.5-17.5 mm. long, 5-7 mm. wide; wings (9.5) 10.5-14.5 mm. long, the claws 3.9-6.5 mm., the blades (6) 7.4-10 mm. long, 2-3.2 mm. wide; keel (9.6) 10-13 mm. long, the claws 3.8-6.8 mm., the blades 5.6-8 mm. long, 2.6-3.3 mm. wide; anthers (0.55) 0.6-0.8 mm. long; stipe of the pod 3-5 mm. long, the body linear- or narrowly oblong-ellipsoid, (8) 10-17 (20) mm. long, 2-4.5 mm. in diameter, smooth or faintly reticulate, glabrous or strigulose; ovules 4—14 (15).
Distribution and Ecology - Plains, prairies, gullied clay hills and knolls, perhaps most abundant in alluvial clay soils of bottomlands and canyon floors but often found on dry gravelly soils of hillsides and benches, adapted to many types of habitat and bedrock but commonest on sedimentary formations, especially sandstones, limestones, and shales, 1900-7600 feet, widespread and all too common over the plains and prairies east of the Rocky Mountains, from the headwaters of the Pecos and Canadian Rivers in northeastern New Mexico north to the Peace River in Alberta and the Pembina in southwestern Manitoba, west across the Continental Divide to upper Clarks Fork in western Montana and just into the Snake River drainage in eastcentral Idaho, and west in New Mexico to the upper Rio Grande Valley; also represented by relatively small-flowered variants in scattered stations around the Colorado and Green River Basins in southwestern Wyoming, western Colorado, central and southwestern Utah, and extreme northcentral Arizona.—Map No. 45.—May to August.
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Discussion
The two-grooved milk-vetch is a handsome floriferous plant, even if inclined to be rankly leafy, and is easily recognized by its connate stipules, basally pouched calyx, and pod of characteristic form. On warm days and while drying in the press, the herbage gives out a strong smell of selenium disagreeable to most people and to some actually nauseating. It is one of the most dangerous and widely dispersed of the seleniferous stock poisons. In its main range to the east of the Divide (and feebly west of it in Montana and Idaho) var. bisulcatus varies little except in the color of the calyx and petals and in pubescence of the fruit. Plants with purple flowers and usually bright red calyces are most common, often occurring in pure stands. These are sometimes mixed with whites or pinkish-lilacs, with which the calyx also varies in depth of coloring from red to almost white and the keel-tip likewise from deeply to faintly maculate. Pure stands of pale-flowered plants are relatively rare, becoming perhaps more frequent from Colorado southward. The pod of var. bisulcatus is ordinarily strigulose, but a glabrous variant is found sporadically from central Colorado northward into Canada. The typus of var. decalvans was apparently of this sort, although Diholcos decalvans as interpreted by Rydberg included a preponderant element of A. racemosus var. longisetus. The following collections represent typical var. bisulcatus and minor variants mentioned up to this point: J. M. Macoun 29,856 (NY); Macoun & Herriott 70,474 (CAS, ND, NY); Hitchcock & Muhlick 11,648 (CAS, NY, RSA, WS), 11,799 (CAS, RSA, WS); C. L. Porter 2779 (NY, RM, TEX, WS, WTU); W. A. Weber 4674 (CAS, SMU, TEX, WS); Clokey 3804 (CAS, NY, WS, the sheet at CAS having partly glabrous, partly pubescent fruits).
On the prairies the flower of var. bisulcatus is relatively large, with banner about 13-17.5 mm. long in all except an occasional starveling individual or in rare depauperate populations, such as occur in exceptionally arid microhabitats; and the ovules are relatively numerous, mostly 5-7 pairs. In the Colorado Basin the two-grooved milk-vetch is represented by a perplexing series of forms with banner 10-14 mm. long and only 2-5 pairs of ovules, which are intermediate in flower-size between the eastern var. bisulcatus and var. Haydenianus. In western Colorado and southern Wyoming the flowers are not only small but also of pale coloring, the calyx-teeth are commonly short (0.7-1.8 mm.), and the plants simulate var. Haydenianus closely, although the pod is smooth or only faintly reticulate and always longer (cf. A. Nelson 3711 = fma. Nelsonii; Ripley & Barneby 5451, 10,603, RSA; Hitchcock & al. 3908, CAS, WS, WTU). In southwestern Utah and adjoining Arizona the form described as A. Haydenianus var. major combines the relatively small flower-size and few-ovulate, smooth pod described above with purple or purplish petals, longer calyx-teeth (as in exactly typical var. bisulcatus), and relatively few (mostly 15-19 as opposed to common counts of 17-29) leaflets. This last form is especially common around the foot of Zion Escarpment (Ripley & Barneby 4795, 4819; Eastwood & Howell 1134, CAS, NY) but extends north to the Sevier Valley in Sanpete County and apparently to Price in Carbon County (Jones 5446, CAS, NY, POM). Having failed in my search for differential characters other than ovule-number to distinguish these forms from the occasional small-flowered variants of var. bisulcatus from east of the Rocky Mountains, I regard them as taxonomically negligible "Basin Variants," a term which I have used freely in annotating specimens.
The reduction of Diholcos micranthus, which has been maintained as a distinct species by Tidestrom and Porter, deserves further comment. The species was originally based on four gatherings from Colorado (all NY!). Two of these, Shear 3569, the specified holotypus, and Clements 100, represent small-flowered forms of var. bisulcatus as defined in these pages; the other two (Tweedy and Smith) are characteristic var. Haydenianus. The description of D. micranthus incorporates the tiny flower (corolla "6-7 mm. long") of the Haydenianus elements and the smooth pod of the other. No example of these two features on one plant is known to exist, so D. micranthus is an illusory concept. Although Porter continued to define his equivalent A. haydenioides in almost the original terms, he distributed at least one collection under the name A. Diholcos (Porter 3239, NY), in which the banner reaches a length of 11 mm. and the body of the pod 14 mm. These plants represent one of the Basin Variants of var. bisulcatus.
The Greene herbarium (ND) possesses two specimens of var. bisulcatus (Wooton 532, from Springer, New Mexico; C. F. Baker 5 in 1901 from westcentral Colorado—more precisely, according to the duplicate at POM, from the Arkansas Valley in Fremont County), filed under the epithets abductus and galericulatus. These proposals of Greene’s were never published.
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Objects
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Distribution
New Mexico United States of America North America| Colorado United States of America North America| Wyoming United States of America North America| Idaho United States of America North America| Montana United States of America North America| Kansas United States of America North America| Nebraska United States of America North America| South Dakota United States of America North America| North Dakota United States of America North America| Manitoba Canada North America| Saskatchewan Canada North America| Alberta Canada North America|