Astragalus lonchocarpus Torr.
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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
"Rocky declivities, near Santa Fe. No. 160."— Holotypus, collected by August Fendler in 1847, GH! isotypi, BM, K, MO, NY, PH!
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Synonyms
Phaca macrocarpa A.Gray, Tragacantha lonchocarpa (Torr.) Kuntze, Homalobus macrocarpus (A.Gray) Rydb., Lonchophaca macrocarpa (A.Gray) Rydb., Astragalus macer A.Nelson, Lonchophaca macra (A.Nelson) Rydb.
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Description
Species Description - Commonly coarse and robust, sometimes quite slender, strigulose throughout or nearly so with fine, filiform or somewhat flattened hairs up to 0.4—0.75 mm. long, the vesture variable in density, the whole plant, or the herbage, or only the growing tips cinereous or gray-silky, or more rarely greenish in part or throughout, the leaflets (when present) either equally pubescent on both sides, or more densely pubescent above than beneath, or sometimes glabrous and minutely red-dotted above; stems several or numerous, erect or diffusely ascending, (2) 3-6 dm. long, together forming low, bushy, or taller, broomlike tufts, subterranean for a space of 1-8 cm., commonly stout and hollow toward the base but sometimes slender and solid or almost so, strictly and repeatedly branched upward from the first emersed node, the primary branches commonly fertile, the secondary and succeeding ones reduced to slender or filiform spurs, these sometimes inserted between a peduncle and its subtending leaf; stipules 1.5-9 mm. long, those at the subterranean, often approximate nodes mostly ovate and comparatively large, stiffly papery, castaneous or purplish, adnate to the suppressed petiole into a subtruncate or bidentate sheath and decurrent around ½ or more of the stem’s circumference, the median and upper ones herbaceous but early turning papery and brownish, with lanceolate or triangular-acuminate, often recurving blades; leaves (2) 4-10 (13) cm. long, with slender, flaccid rachis, some of the lowest (usually) with 3-9 (11) distant, commonly scattered, linear or linear-oblanceolate, obtuse or subacute, involute or almost flat leaflets 2-25 (36) mm. long, the terminal one confluent with the rachis and commonly distant from and longer than the last pair, but the lateral leaflets of most upper (sometimes all) leaves reduced in number, length, or both, or wanting, the leaf then consisting of a naked rachis terminating in an obscurely expanded phyllode; peduncles stiffly erect or incurved-ascending, (6) 9-22 cm. long, the first 1 or 2 usually long and stout, the racemes (or most of them) projected well beyond the main stem-axis; racemes loosely, often interruptedly (7) 15-35 (55)- flowered, the flowers ± secundly nodding, the axis (3.5) 5—20 cm. long in fruit; bracts papery-membranous, ovate-acuminate or lanceolate, 0.8-2.5 mm. long; pedicels at earliest anthesis ascending, (1.3) 1.8-3 mm. long, early arched outward, horizontal, decurved, or abruptly deflexed, in fruit (2) 3-4 (4.5) mm. long; bracteoles 0; calyx (5.8) 6.5-10 mm. long, strigulose with white, rarely mixed with a few black hairs, the oblique disc (0.7) 1-1.7 mm. deep, the cylindric, cylindro-campanulate, rarely campanulate, reddish or pallid tube (5) 6—8 mm. long, 2.7-4 mm. in diameter, oblique at base or sometimes a trifle turgid or even gibbous dorsally, the subulate or triangular-subulate teeth (0.6) 1—2 mm. long, all crowded toward the dorsal side, the ventral pair broadest, separated by a wide, often deeply cut-back sinus; petals cream-colored or almost white (reportedly sometimes purplish, Jones); banner recurved through ± 50°, 13.5—19.5 mm. long, variable in outline, the long-tapering claw gradually or abruptly expanded into a broadly to narrowly rhombic-ovate, shallowly notched or scarcely emarginate blade 6-10 mm. wide; wings as long or slightly shorter, the claws (6.3) 7-9.5 mm., the oblong, lance-oblong, or linear, obtuse or subemarginate blades 7.5—10 (12.5) mm. long; keel 10.5-14 mm. long, the claws (6.2) 7-9.4 mm., the lunate blades 4.2-6.5 mm. long, 2.3-2.8 mm. wide, incurved through 90-95° to the deltoid or triangular, obtuse, sometimes slightly porrect apex; anthers 0.5—0.75 mm. long; pod pendulous, stipitate, the slender, straight stipe (3) 5—12 (15) mm. long, the body linear-oblanceolate, -elliptic, or -oblong in profile, 2.2—4.7 cm. long, 3.3—6 mm. in diameter, straight or more often gently decurved, long-acuminate downward into the stipe, sometimes equally long-acuminate upward but usually narrowly cuneate distally and cuspidate at apex, strongly obcompressed, the low- convex ventral face, or both faces, carinate by the sutures, the dorsal face sometimes flat or shallowly excavated, the lateral angles narrow but obtuse, the thinly fleshy, green or red-dotted, glabrous or rarely puberulent valves becoming stiffly papery, brown, smooth or faintly cross-reticulate and rarely striate lengthwise, ovules (12) 16-26; seeds brown, smooth, 3.5-4 long.
Distribution and Ecology - Gullied bluffs and badlands, open gravelly or sandy hillsides in juniper-pinon woodland, most commonly in alkaline soils derived from sandstone, but occasionally on limestone, rarely on granitic bedrock, 4900-7800 feet, widespread and locally abundant over the Colorado Basin southward from Tavaputs Escarpment in Utah and western Colorado, extending less frequently west across Utah into northeastern and eastcentral Nevada, and, still fairly common, southeast, barely entering extreme northeastern Arizona, over the Continental Divide into the Rio Grande and Pecos Valleys in northwestern and central New Mexico, thence north, around the south flanks of the Rocky Mountains, to the upper Canadian, and to the Arkansas on the east slope in Colorado; in western Colorado extending rarely north to the eastern edge of the Uintah Basin in Rio Blanco County.—Map No. 23.—May to July.
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Discussion
The great rushy milk-vetch, A. lonchocarpus, has so strong an individual character that once seen it is never forgotten. The sparse herbage, appearing wiry but actually soft and flaccid to the touch, the nodding, pearly-white or cream-colored flowers, and the long, narrow, pendulous pods are distinctive features. Both calyx and pod are often tinged with a bright reddish color which turns brown on drying. The pod dehisces downward through the length of the ventral suture and the valves fold outward like the covers of a book, forming an oddly leaflike structure after the seeds are shed.
A certain degree of variation, implicit in the foregoing description, must be expected in a species as widely dispersed as A. lonchocarpus, and only a few points require comment. The plants found at low elevations in the intermountain deserts tend to be robust, with stout hollow stems and a markedly ephedroid aspect, due to great reduction of the leaflets. A slender form, with narrow pod and narrow solid stems, has been described as A. macer; it is found here and there throughout the range of the species and is interpreted as a minor variant. The actual typus of A. lonchocarpus is closer to Lonchophaca macra, as defined by Rydberg, than to the coarse Basin variants with which he and A. Nelson associated the earlier name. A thinly pubescent form with glabrous or glabrescent upper leaf-surface occurs in a small area in northwestern New Mexico and adjoining Colorado, but even in its compact range does not replace (and passes into) the common cinereous state. A puberulent pod is found rarely in southwestern Colorado but is sympatric with the common glabrous form. It is interesting to find that A. lonchocarpus is most abundant and also most variable on the southwest flank of the Rocky Mountains, the region that has yielded its two rare relatives A. Schmollae and A. Ripleyi, and lies close to the center of its own far-flung range. The peripheral populations of A. lonchocarpus in Nevada and east of the Divide in Colorado are closely similar in detail. It seems a natural inference that the genuine Lonchocarpi had their point of origin in the upper San Juan Valley or thereabouts and that A. lonchocarpus has spread radially thence along available paths of migration, carrying with it a decreasing potential for mutation.
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Objects
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Distribution
Colorado United States of America North America| Utah United States of America North America| Nevada United States of America North America| Arizona United States of America North America| New Mexico United States of America North America|