Astragalus coriaceus Hemsl.
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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
"North Mexico, Zacatecas (Coulter). Hb. Kew."— Holotypus, K!
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Synonyms
Pisophaca coriacea (Hemsl.) Rydb., Astragalus antoninus S.Watson, Pisophaca antonina (S.Watson) Rydb.
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Description
Species Description - Slender, diffuse or ascending, rather sparsely leafy, strigulose with appressed or subappressed hairs up to 0.25-0.45 mm. long, the herbage green or greenish- cinereous, the leaflets bicolored, brighter green and usually glabrous above or nearly so, rarely pubescent on both sides; stems several, 1.5-3.5 dm. long, naked and subterranean for a space of 1-15 cm., commonly branched on emergence, sometimes simple; stipules dimorphic, the lowest amplexicaul and connate into a subtruncate or bidentate sheath 1-2 mm. long, the median and upper ones lanceolate or triangular-acuminate, almost or fully amplexicaul, united by a mere line; leaves (2) 3.5-9 cm. long, subsessile, or the lowest shortly petioled, with 11-23 rather distant, oblanceolate or linear-oblanceolate, obtuse or retuse, flat or folded leaflets 2-20 mm. long; peduncles divaricate or incurved-ascending, (4) 5-14 cm. long, longer than the leaf; racemes loosely 5-12 (16)-flowered, the flowers erect- ascending, the axis becoming (1.5) 2—8 cm. long in fruit; bracts submembranous, triangular or nearly so, 1—2.5 mm. long; pedicels ascending, straight or nearly so, at anthesis 1—1.5 mm. long, in fruit a little thickened, 1.4-3 mm. long; bracteoles 0-2, minute when present; calyx 5.8—8.6 mm. long, strigulose with black, white, or mixed black and white hairs, the oblique disc 1.1—1.9 mm. deep, the cylindric or cylindro-campanulate tube (4.5) 5—6.2 mm. long, 2.1-3 mm. (3.4) in diameter, the subulate or lance-subulate teeth (1) 1.5—3 mm. long; petals pink-purple or purplish; banner gently recurved through ± 45°, broadly rhombic-oblanceolate or rhombic, notched at apex, (13) 14-17 mm. long, 5.5-8.4 (10) mm. wide; wings (12) 13-15.2 mm. long, the claws 4.3-7 mm., the elliptic-oblanceolate, obtuse, erose-emarginate, or shallowly retuse, slightly incurved blades 8-9.6 mm. long, 2.5-3.3 mm. wide; keel 10-13 mm. long, the claws 4.1-6.5 mm., the half-obovate blades 5.8-7 mm. long, 2.5-3.3 mm. wide, incurved through 80-90° to the blunt apex; anthers 0.6-0.7 mm. long; pod erect, sessile or nearly so, sometimes contracted at base into a stipelike neck up to 1 mm. long, the body obliquely ovoid or ovoid-ellipsoid, turgid to decidedly inflated, either obtuse or turbinate at base, shortly deltoid or more rarely long-acuminate distally, (1.2) 1.4-2.2 (2.4) cm. long, (5) 6-9 mm. in diameter, slightly obcompressed, the thinly fleshy, green, minutely black- or white-strigulose valves becoming stiffly papery or almost leathery, castaneous, cross-reticulate; dehiscence apical; ovules 20-30; seeds (seldom seen) dark brown, sparsely or closely pitted, dull, 2.1-2.8 mm. long.
Distribution and Ecology - Dry open hillsides, on sandstone and limestone, ± 6500-10,000 feet, perhaps sometimes lower, in desert scrub, yucca- or mesquite-grassland, or in openings of oak or pine forest, apparently not uncommon, southeastern Chihuahua to northern and western Zacatecas, southern Coahuila, southern Nuevo Leon, and western San Luis Potosi.—Map No. 18.—June to November, the fruits long persisting.
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Discussion
The leathery milk-vetch, A. coriaceus, stands apart from other Scytocarpi because of its ascending or erect flowers followed by fruits similarly erect on stiffly ascending pedicels. The habit of growth is similar to that of A. flexuosus, but A. coriaceus differs from all the genuine Scytocarpi in its large flowers. The flower-size suggests the next subsect. Halliani, but this differs in the broader calyx and ordinarily nodding or humistrate pod. The species appears to be less variable in its pubescence and other features than the majority of Scytocarpi, but it has been collected comparatively seldom and the full range of variation has probably not been sampled.
Jones already suspected that A. coriaceus and A. antoninus were conspecific. The typus of A. coriaceus (cf. phototypus, NY) is fragmentary and poorly preserved, but there is no doubt about its identity. During the preliminary studies I annotated most of the material in United States herbaria as A. antoninus, the genuine A. coriaceus being at the time unknown to me.
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Objects
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Distribution
Chihuahua Mexico North America| Coahuila Mexico North America| Durango Mexico North America| Zacatecas Mexico North America| Nuevo León Mexico North America| San Luis Potosí Mexico North America|