Astragalus pectinatus Douglas ex G.Don
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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
"Native of North America, in the pastures of the Saskatchewan."—Holotypus, formerly in herb. Lambert., not found at BM, but the description and following reference decisive.
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Synonyms
Phaca pectinata Hook., Tragacantha pectinata (Hook.) Kuntze, Ctenophyllum pectinatum (Hook.) Rydb., Cnemidophacos pectinatus (Hook.) Rydb.
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Description
Species Description - Relatively coarse, diffuse, with a thick, woody taproot and pluricipital root- crown, strigulose nearly throughout with fine, appressed and narrowly ascending hairs up to 0.2-0.6 mm. long, the base of the stems, the upper surface of the leaflets, and the pod glabrous, the plentiful but stiff and narrow foliage pale gray-green, sometimes cinereous in youth; stems commonly stout, (1) 1.5-6 dm. long, decumbent or prostrate with ascending tips, forming depressed, bushy mats, diffusely and subpaniculately branched at or below the middle, rarely simple; stipules 1.5 10 mm. long, dimorphic, those at the lowest leafless nodes larger than the rest, amplexicaul and connate into a papery, shortly bidentate sheath, passing upward into shorter, herbaceous ones connate at base only or finally decurrent and free, the deltoid-acuminate blades commonly squarrose; leaves sessile or nearly so, 4-11 cm. long, with rigid, canaliculate, usually incurved rachis and (2) 4-7 (10) pairs of opposite or somewhat scattered, linear, filiform, or rarely linear-oblanceolate, involute and dorsally carinate, at length stiff and falcately incurved leaflets (7) 15-70 mm. long, sometimes narrowed at base into a short pseudopetiolule but not jointed, the lowest pair often longer than the rachis, the terminal one continuous with and similar in form to the rachis, mostly longer than the last lateral pair; peduncles stout, often incurved-ascending, (2) 3.5-8 (10.5) cm. long; racemes (7) 12-30-flowered, rather dense at early anthesis, the flowers at first ascending, later horizontal and finally declined, the axis elongating, 3-13 (17) cm. long in fruit; bracts herbaceous becoming papery, lanceolate or lance-acuminate, 2-7 mm. long; pedicels at anthesis 2-3 (3.5) mm. long, in fruit becoming thickened, rigid, arcuate or twisted and recurved, 2.5-5 mm. long; bracetoles usually 0; calyx 8-12 mm. long, strigulose with black, white, or mixed hairs, the oblique disc 1.1-2 mm. deep, the cylindric tube 6.5-9 mm. long, 2.8-4.3 mm. in diameter, the subulate or lanceolate teeth 1.5-3 mm. long, the whole becoming thinly scarious, ruptured, marcescent; petals ochroleucous, drying yellowish or cream-colored; banner gently recurved through 40-45°, 21-24 mm. long, the narrowly cuneate claw expanded into a lance-ovate, deeply notched blade 6.6-9.8 mm. wide; wings 17.7-19.5 mm. long, the claws 7.2-9 mm., the narrowly oblong-oblanceolate, obtuse, nearly straight blades 10.3-12 mm. long, (1.8) 2.7—3.4 mm, wide; keel 13.8-16 mm. long, the claws 7.9-9 mm., the lunately half-obovate or half-oval blades 6.3-7.5 mm. long, 3-3.5 mm. wide, gently incurved through 75-85 (90)° to the obtuse apex; anthers 0.7-0.85 (0.9) mm. long; pod declined or deflexed, sessile, plumply ellipsoid, or oblong- or rarely clavate-ellipsoid, straight or slightly decurved, (1) 1.5-2.5 cm. long, (4.5) 5-8 mm. in diameter, obtuse at base, abruptly contracted distally and long-cuspidate at apex, normally a trifle obcompressed and somewhat flattened dorsally but (when short) sometimes a little laterally compressed, both the sutures thick, salient, and cordlike, the ventral one 1—1.5 mm. wide, the dorsal one narrower, often sinuate, the green, fleshy, lustrous, glabrous valves becoming stiffly leathery or woody, stramineous or brownish, rugulose-reticulate, not inflexed; ovules (23) 26—32; seeds pale or pinkish-brown, smooth or minutely pitted, lustrous, 3-3.6 mm. long.
Distribution and Ecology - Alkaline clay or sandy flats, gullied bluffs, and low, barren hilltops, commonly in alluvial soils derived from shale outcrops, 1600-7800 feet, widely dispersed and locally common over the higher prairies and plains from southern Alberta to extreme southwestern Manitoba, south to the valley of the Arkansas River in Kansas and the the Mesa de Mayo in Colorado (and to be expected in adjoining New Mexico), west in Montana to Glacier Park and the upper Missouri Valley and in Wyoming to Yellowstone Park and the valley of the North Platte; reported, probably in error, from Utah (Rydb., 1929, p. 288).—Map No. 48.— May to July, the fruit long persisting.
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Discussion
The tine-leaved milk-vetch, A. pectinatus, is one of the most distinctive North American Astragali. Its leaves, composed of about four to seven or rarely ten pairs of extremely long, narrow, stiffly incurved leaflets, might be likened to those of A. Kentrophyta on a greatly enlarged scale but have no exact counterpart in the genus. Except for some inevitable variation in size of the flowers and in size and outline of the pods, A. pectinatus is a stable species and in spite of its wide dispersal, both in latitude and altitude, shows no signs of racial differentiation.
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Objects
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Distribution
Alberta Canada North America| Saskatchewan Canada North America| Manitoba Canada North America| North Dakota United States of America North America| Nebraska United States of America North America| Kansas United States of America North America| Colorado United States of America North America| Wyoming United States of America North America| Montana United States of America North America|