Astragalus strigulosus Kunth
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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
"Crescit in temperatis Regni Mexicani, prope Moran, alt. 1330 hex."—Typus, collected in 1803 by Alexander von Humboldt and Aime Bonpland, P (herb. H. B. K.)!—Moran, or Real de Moran, is in s. Hidalgo, between Pachuca and Actopan, acc. Sprague in Kew Bull.
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Synonyms
Tragacantha strigulosa (Kunth) Kuntze, Atelophragma strigulosum (Kunth) Rydb.
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Description
Species Description - Coarse, leafy, caulescent perennial, with a taproot and (probably, but seldom observed) shortly subterranean caudex, strigose-pilosulous nearly throughout with rather stiff, subappressed or narrowly incurved-ascending hairs up to 0.4-0.7 mm. long, the herbage cinereous or canescent in youth, sometimes greenish in age, the leaflets glabrous or marginally pubescent above; stems erect and ascending in clumps, 2-6 dm. long (perhaps longer late in the season), simple or branched at several nodes from near the base upward; stipules 3-9 mm. long, more or less dimorphic, the lowest connate through half their length or more into a papery- scarious sheath sometimes ruptured or even deciduous in age, the upper ones longer, lanceolate or deltoid-acuminate, either connate at base, or semiamplexicaul- decurrent and free; leaves 4-10 cm. long, subsessile, with 13-23 (29) oblong- oblanceolate, broadly or narrowly oblong-elliptic, obtuse and mucronulate, retuse, or rarely subacute, flat or loosely folded leaflets 6-18 (22) mm. long; peduncles rather stout, erect or incurved-ascending, (4) 5-10 cm. long, a little longer or shorter than the leaf; racemes (12) 15-35 (40)-flowered, dense in early anthesis, the flowers early declined and retrorsely imbricated, the axis somewhat elongating, (1.5) 2-9 cm. long in fruit; bracts membranous, pallid, linear-lanceolate, (1.5) 2-4.5 mm. long; pedicels at anthesis 0.5-1 mm. long, early arched outward and downward, in fruit thickened, 0.8-2 mm. long; bracteoles 0-2, commonly 0; calyx (5.2) 5.8-7.5 mm. long, pilosulous with black, fuscous, or mixed black and white hairs, the oblique disc 0.6-1 mm. deep, the campanulate tube 2.8-3.2 mm. long, (2.2) 2.5-2.8 mm. in diameter, the slenderly lance-subulate teeth (2.5) 3-4.3 mm. long, the ventral pair often shorter than the rest, the whole becoming papery, marcescent unruptured; petals ochroleucous, immaculate; banner gently recurved through ± 40°, rhombic-obovate, obovate-spatulate, or elliptic-oblanceolate, shallowly or deeply notched, 9.2—11.5 mm. long, (4.2) 4.6—6 mm. wide; wings (7.7) 8.5-10.5 mm. long, the claws 3-3.5 mm., the narrowly oblanceolate, obtuse and erose, or obliquely truncate or emarginate, slightly incurved blades (5.5) 6-7.5 mm. long, (1.8) 2-2.5 mm. wide; keel 6.7-7.5 mm. long, the claws 3.1-3.5 mm., the half-obovate blades 4.2—4.7 mm. long, 2.1—2.6 mm. wide, abruptly incurved through 85-95° to the rounded, or more rarely deltoid and obtusely apiculate apex; anthers 0.4-0.55 mm. long; pod pendulous, stipitate, the stipe 2-4 mm. long, the body ellipsoid to plumply oblong-ellipsoid, 12-17 (20) mm. long, (4.5) 5-7 mm. in diameter, about 2—3 times longer than wide, straight or a trifle decurved, broadly cuneate at both ends, shortly apiculate-beaked, dorsiventrally compressed, low- carinate ventrally by the suture, openly sulcate dorsally, the thinly fleshy, green, glabrous or (rarely) white- or black-puberulent valves becoming rather stiffly papery, stramineous, cross-reticulate, inflexed as an incomplete or nearly complete septum 0.8-1.6 mm. wide; dehiscence basal and upward through the proximal half of the dorsal suture and the septum; ovules 14-18 (19); seeds brown or olivaceous, dull, smooth, 1.8—2.1 mm. long.
Distribution and Ecology - Dry, open hillsides and mesas, on either calcareous or volcanic bedrock, about 7000 to 8650 feet, apparently rather local, Valley of Mexico (State and D. F.), southern Hidalgo, and northwestern Oaxaca.—Map No. 8.—May to November.
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Discussion
Although historically the prototype of its section, A. strigulosus is a comparatively rare and local species which has often been misinterpreted and never adequately disentangled from the related A. guatemalensis; the record has become badly confused by the use of the epithet strigulosus for almost any Mexican species at all similar in general fades. Thus among the collections cited by Hemsley (1880, p. 266) are several now referred to A. guatemalensis var. brevidentatus, and an isotypus of A. potosinus. So far as I can learn, Jones (1923) included A. strigulosus of this work in his A. guatemalensis, transferring the epithet to a vaguely defined, small-flowered astragalus akin to A. Rusbyi which represents a type of Strigulosi found in northcentral Mexico and southwestern United States but absent from the central plateau, (see our A. longissimus). Likewise Rydberg (1928, p. 158) listed as Atelophragma strigulosum a mixture of the genuine species and A. guatemalensis var. brevidentatus (e.g. Purpus 2681, 3209; E. W. Nelson 1427, all NY, US). Apparently his reliance on a longer stipe as the best diagnostic character of A. strigulosus led him into error, for there is some overlapping between the two species in this respect. In the foregoing key I have pointed out what seems to be a significant difference in the dehiscence of the pod, but in practice A. strigulosus is more easily distinguished from A. guatemalensis var. brevidentatus by its ochroleucous flowers and longtoothed, loosely black- or fuscous-hairy calyx. It is also a more erect and sturdy plant, apparently confined to sunny situations in the valleys and open foothills, whereas A. guatemalensis is found in a cooler environment of pine woods and shady ravines or barrancas in the mountains. The species varies little. The pod, as originally described, is normally glabrous, but there is one collection from near the type-locality in Hidalgo (10 miles south of Actopan, Fearing & Thompson 84, TEX) in which the valves are beset with very short, scattered hairs, either wholly black or black and white intermingled. Minor variants of the same sort are known in A. tolucanus and A. guatemalensis var. brevidentatus.
Specimens apparently referable to A. strigulosus but too young for certain determination were collected by Parry & Palmer (No. 169, GH, NY) ostensibly in the region of San Luis Potosí, where A. potosinus and A. tioides are the Strigulosi most likely to be encountered. Pending verification of the record, which may be based in error, I have omitted this range extension from the map.
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Objects
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Distribution
Hidalgo Mexico North America| México Mexico North America| Distrito Federal Mexico North America| Puebla Mexico North America| Oaxaca Mexico North America|