Astragalus cyaneus A.Gray
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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
"148. Sante Fe, on gravelly hills and low mountains among rocks."—Holotypus, Fendler’s Pl. Novo-Mexicanae No. 148, collected in 1847, GH! isotypi, NY, PH, US!
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Synonyms
Tragacantha cyanea (A.Gray) Kuntze, Astragalus shortianus var. cyaneus (A.Gray) M.E.Jones, Xylophacos cyaneus (A.Gray) Rydb., Astragalus jemensis A.Nelson
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Description
Species Description - Low but robust, acaulescent or nearly so, with a thick, woody taproot and shortly forking, at length knotty caudex, strigulose throughout with straight, appressed or subappressed, filiform or slightly flattened hairs up to 0.4—0.75 mm. long, the herbage cinereous or greenish, the leaflets pubescent on both sides, but of a brighter green beneath the vesture above; stems several, either reduced to crowns or a little developed and up to 6 cm. long, but always shorter than the leaves, and the internodes not over 1.5 cm. long; stipules pallid, papery or early becoming so, several-nerved, lanceolate, triangular, or triangular-acuminate, 4—9 mm. long, decurrent around ½ to the whole stem’s circumerence, free; leaves 6—18 cm. long, with stiff, grooved petiole and (15) 17-29 obovate to elliptic, obtuse, acute, or sometimes retuse, flat leaflets 4—19 mm. long; peduncles stout, (4) 6-13 cm. long, a little shorter than the leaves, ascending at anthesis, arcuately reclining or prostrate and radiating in fruit; racemes loosely (9) 12-22 (25)- flowered, the flowers loosely spreading or sometimes declined in age (but not characteristically nodding), the axis somewhat elongating, (2) 4-14 (20) cm. long in fruit; bracts thinly herbaceous becoming papery-membranous, lanceolate or linear-acuminate, 2.5-6 mm. long; pedicels erect or ascending, straight or nearly so, at anthesis 1-2.5 mm., in fruit clavately thickened, 2.5-4.5 mm. long; bracteoles 2, conspicuous or sometimes rudimentary; calyx 11.3-15 mm. long, strigulose with mixed black and white hairs, the oblique disc 2-2.8 mm. deep, the usually purplish, cylindric, or deeply and broadly campanulate tube 8.2-10.6 mm. long, 3.7-5.8 mm. in diameter, the subulate or lance-subulate teeth 2.3—4.6 mm. long; petals pink-purple, the banner with a pale, striate eye; banner gently recurved through ± 40°, spatulate-oblanceolate or ovate-cuneate, shallowly notched, 18-22 mm. long, 9.2-11 mm. wide; wings 17.9-21.9 mm. long, the claws 8.2-10.6 mm., the narrowly oblong, obtuse or obscurely emarginate, nearly straight blades 11.2-13.6 mm. long, 3.1-3.6 mm. wide; keel 16.3-18 mm. long, the claws 9-10.7 mm., the lunately half-elliptic or half-obovate blades 7.3-8.7 mm. long, 3.4-4 mm. wide, incurved through 90-95° to the bluntly deltoid apex; anthers 0.65-0.8 mm. long; pod ascending (humistrate), obliquely oblong-ellipsoid, 2.5-5 cm. long, 7-13 mm. in diameter, gently incurved, obtuse at base, obcompressed through the lower ¾ or more and thence passing upward into a triangular- or lance-acuminate, laterally compressed, cuspidate beak, openly sulcate along both sutures, both sutures prominent and cordlike, the ventral one stouter, the green or purple-tinged, thickly fleshy, strigulose valves becoming rigidly woody, strongly reticulate, stramineous or brownish, 1-2 mm. thick when fully ripe, inflexed behind the dorsal suture to ± the depth of the valve-wall, the septum forming a narrowly tubular or triquetrous cavity the length of the pod-body, the sutures subcontiguous within, the cross-section therefore didymous; dehiscence apical, tardy, after falling; ovules (35) 39-48; seeds brown, smooth but dull, 2.7-3.4 mm. long.
Distribution and Ecology - Dry hillsides and gullied banks, in sandy or gravelly granitic soils, commonly associated with piñon and juniper, 6900-7300 feet, locally plentiful but uncommon, known only from the east side of the Rio Grande Valley in Santa Fe, Taos, and possibly northeastern Bernalillo Counties, New Mexico.—Map No. 82.—Late April to June.
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Discussion
The cyanic milk-vetch is a rather coarse astragalus, although handsome when in flower and memorable later on for its extremely large, thickly fleshy, ultimately woody pods. The history of A. cyaneus has been recounted elsewhere (Barneby, 1947, p. 455, as A. Shortianus var.), and it is shown there how a wide range based on misidentified material of related species was at one time attributed to what is now known to be a narrow endemic of the upper Rio Grande Valley. The cyanic milk-vetch is closely related to A. Shortianus, from which it is artificially separated in the subsectional key by the leaflet number, a useful but systematically unimportant character. It is distinguished further by the shorter, often flattened hairs of the herbage, the elongating raceme-axis, and the strigulose rather than villous calyx, features which combine with the numerous leaflets to create a wholly individual aspect, amply sufficient in the context of the section to maintain A. cyaneus in the rank of species. The main range of A. Shortianus lies well to the north of A. cyaneus, but it has been collected once near Santa Fe, the type- locality of its relative. The specimens from this outlying station are wholly typical, showing no suggestion of passage into A. cyaneus.
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Objects
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Distribution
New Mexico United States of America North America|