Astragalus beathii Ced.Porter
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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
Type. Two miles south of Cameron, Coconino County, Arizona, June 14, 1939, L. N. Goodding Sel. 34-39... " Holotypus, RM! isotypi, ARIZ, MO!
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Description
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Species Description - Coarsely robust, ill-scented perennial, nearly glabrous below but becoming strigulose distally with filiform, or flattened and scalelike, appressed or subappressed hairs up to 0.35-0.7 mm. long, the herbage deep green, the leaflets of the lower leaves often glabrous on both sides, those of the upper ones glabrous above; stems several or numerous, (1.5) 2-6 dm. long, mostly stout and fistular toward the base, striate or sulcate, purple-tinged becoming stramineous, simple or nearly so; stipules submembranous, greenish or purplish, early becoming pallid and papery-scarious, 3-9.5 mm. long, strongly decurrent around half, or the lowest around nearly the whole stem’s circumference, the broadly deltoid or triangular- acuminate blades mostly reflexed; leaves 6-12 (15) cm. long, shortly petioled, with 11-21 (23) narrowly elliptic-oblanceolate and obtuse varying into broadly obovate or oblong-obovate and retuse, flat, thick-textured leaflets 5-25 mm. long; peduncles stout, incurved-ascending, (2.5) 4-10 cm. long, a little shorter, or the first a little longer than the leaf; racemes 10-27-flowered, rather dense at first anthesis, the flowers ultimately spreading-ascending, the axis 3.5-10 cm. long in fruit; bracts membranous or broadly membranous-margined, ovate-triangular, or lanceolate, 2-4.2 mm. long; pedicels at anthesis straight, ascending, 0.9-2 (2.5) mm., in fruit greatly thickened, arched outward, 2.2-3 mm. long; bracteoles commonly 2, usually conspicuous, rarely 0; calyx (7.7) 8.2-10.5 mm. long, either densely or only minutely and sparsely black- (rarely white-) strigulose, the slightly oblique disc (1.3) 1.5—2 mm. deep, the membranous, campanulate or subcylindric, purplish or deep reddish-purple tube (5.3) 5.7-7.8 mm. long, (3) 3.4-4.5 (5) mm. in diameter, the triangular-subulate teeth (1.8) 2-3.1 mm. long, the ventral pair often broadest and shortest, the whole becoming papery, ruptured, marcescent; petals bright purple (drying violet), the wing-tips paler or white, more rarely all pure white, or "pale-blue"; banner recurved through ± 40°, broadly rhombic- elliptic or -ovate, shallowly or deeply notched, (17) 20-25 (27.7) mm. long, (8.5) 10-12 mm. wide; wings (13.4) 15.4-19.5 (21.8) mm. long, the claws (6) 6.5—8.2 mm., the oblong-oblanceolate or linear-oblong, obtuse, obliquely truncate, or obscurely emarginate, nearly straight blades (8.5) 11-14.8 (16.9) mm. long, (2.6) 3.1-4.1 mm. wide; keel (9.6) 11.2-16.4 mm. long, the claws (6.2) 6.8-9 mm., the lunately half-elliptic blades (7.1) 7.5-10.2 mm. long, 3.2-4.2 mm wide, incurved through 45-80° to the bluntly triangular apex; anthers (0.7) 0.8-1 mm. long; pod deflexed or declined, sessile or nearly so (the stipe not over 0.6 mm. long, nor longer than wide), narrowly to plumply oblong-ellipsoid, straight or a trifle incurved, (2) 2.5—3.9 cm. long, 7—11 mm. in diameter, cuneately attenuate at base, abruptly contracted distally into a triangular, rigidly cuspidate beak, subterete when first formed, becoming a little obcompressed when dry, flattened or low-convex ventrally, flattened or shallowly grooved dorsally, the sutures both thick and cordlike, the dorsal one sometimes undulate, the thick, fleshy, green or purplish-green, glabrous or minutely strigulose, inwardly pulpy-filamentous valves becoming stiffly leathery, stramineous, cross-reticulate and wrinkled lengthwise, inflexed as a narrow septum 1.3-2.3 mm. wide; dehiscence apical and downward through the ventral suture, the beak slightly gaping; ovules 29-52; seeds ocher- or chestnut-brown, sometimes purple-dotted, smooth but dull, 3.2-4.1 mm. long.
Distribution and Ecology - Sandy flats, red clay knolls, and gullied washes in badlands, on selenium- bearing soils derived from sandstone, 4000-4800 feet, forming extensive and conspicuous colonies but extremely local, known only from the lower valley of the Little Colorado River within a radius of ± 6-7 miles of Cameron, Coconino County, Arizona.—Map No. 72.—Late March to May, the fruit long persistent on withered stems.
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Discussion
The Beath milk-vetch is a coarse, nevertheless handsome species, remarkable for its narrow range and for the amount of variation encompassed within the few populations known to exist. In several respects it is intermediate between subsect. Preussiani and subsect. Pattersoniani, combining the ascending, normally purple flower of the former with the succulent, ultimately subligneous, inwardly pulpy-filamentous pod of the latter. The pod vanes greatly in size and may be either glabrous or puberulent, and the ovules vary in number from about fifteen to twenty-five pairs. The calyx is ordinarily purplish or deep reddish-purple, but the petals vary from a vivid shade of purple, which turns violet in drying, through successively paler shades of lavender-purple into a pure albino white. The variation is of a sort that might reasonably be expected of an imperfectly stabilized hybrid involving some forms of A. praelongus and A. Preussii. Typical A. praelongus, which might supply the factors for a spreading, sessile, semibilocular pod of succulent texture, sometimes white flowers and sometime numerous ovules, widely dispersed over northern Arizona and has been collected close to Cameron in the direction of Tuba City. The var. Preussii, relatively few-ovulate and closely resembling A. Beathii in form, orientation, and normal coloring of the flowers, is rare in Arizona and not know to occur within fifty miles of the Painted Desert. However its range as traced up to the present is discontinuous, and stations along the Colorado between Navajo Bridge and southern Nevada are to be expected.
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Objects
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Distribution
Arizona United States of America North America|