Monographs Details: Astragalus reflexus Torr. & A.Gray
Authors:Rupert C. Barneby
Authority: Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(2): 597-1188.
Family:Fabaceae
Discussion:

356.  Astragalus reflexus

Precocious winter-annual, variable in stature according to site and season, commonly slender, thinly hirsute-hirsutulous (especially upward) with rather stiff, straight, horizontal or widely ascending hairs up to 0.8-1.3 mm. long, the herbage green, the leaflets glabrous above; stems solitary and erect, or more often 3-several and diffuse or ascending from a slender or filiform taproot, 1-3.5 dm. long, either simple or (when robust) branched and spurred below the first peduncle; stipules (2) 2.5-7 mm. long, the lowest ones papery-scarious or early becoming so, semi- or almost fully amplexicaul but free, the upper ones herbaceous, larger and wider, ovate or broadly lanceolate, glabrous dorsally, the margins ciliate and often beset with a few thickened processes; leaves 2-8 cm. long, the lowest shortly petioled, the rest commonly subsessile, with (9) 11-15 (19) oblong-ovate, -obovate, or obovate-cuneate, sharply retuse, flat, thin-textured leaflets (3) 5-15 mm. long; peduncles erect or incurved-ascending, (3) 4-8.5 cm. long, equaling or well surpassing the leaf; racemes loosely but shortly 3-10-flowered, the flowers early spreading, ultimately declined, the axis little elongating, 4-10 mm. long in fruit, the pods loosely retrorse-imbricated; bracts membranous, triangular or triangular-acuminate, 0.5-1.1 mm. long, ciliate; pedicels at anthesis ascending, 0.5-1.1 mm. long, becoming somewhat thickened, arched outward, 0.7-1.4 mm. long in fruit, persistent; bracteoles 0; calyx 1.9-2.7 mm. long, thinly white-pilosulous, the subsymmetric disc 0.3-0.5 mm. deep, the shallowly campanulate tube 1.1-1.5 mm. long, 1.2-1.5 mm. in diameter, the subulate teeth 0.7-1.2 mm. long, the whole becoming papery, ruptured, marcescent; petals bicolored, the banner and keel bluish- or reddish- violet, the wings pallid or white-tipped or -margined; banner gently recurved through ± 40°, ovate- or elliptic-cuneate, 4.2-5.2 mm. long, 2.1-3.4 mm. wide, shallowly emarginate, the sinus mucronulate; wings (0.9-1.5 mm. shorter than the keel) 3.1-4 mm. long, the claws 0.9-1.2 mm., the narrowly oblanceolate, obtuse, slightly incurved blades 2.5-3.2 mm. long, 0.7-1.1 mm. wide; keel (a trifle shorter or longer than the banner) 4.3-5 mm. long, the claws 1.1—1.4 mm., the lunately lanceolate blades 3.2-3.7 mm. long, 1.1—1.5 mm. wide, gently incurved through ±40° and gradually tapering into a narrow, beaklike, ultimately obtuse apex; anthers 0.15-0.3 mm. long; pod reflexed, sessile on and disjointing from an obscure gynophore 0.1—0.5 mm. long, the body narrowly to broadly ovate or triangular-ovate in dorsiventral view, 5.5—9 mm. long, 2.5—5.5 mm. in diameter, truncate or shallowly retuse at base, abruptly contracted distally into a subulate cusp about 0.5 mm. long, triquetrously compressed, carinate ventrally by the prominent, straight or slightly incurved suture, deeply and openly sulcate dorsally, the pale green or commonly purple-speckled, glabrous valves becoming brownish, stiffly papery, prominently cross-reticulate and somewhat rugulose on the obtuse lateral angles, inflexed as a complete but narrow septum 0.4—1 mm. wide; seeds orange-brown or greenish, smooth but scarcely lustrous, 1.9—2.1 mm. long. Collections: 18 (o); representative: F. H. Wagner 58 (SMU, TEX); Ruth 722 (SMU, WIS); Reverchon 1950 (SMU), distrib. Curtiss 594* (ND, NY); E. Hall 151 (NY); Shinners 14,174 (RSA, SMU).

Prairies and roadsides, on calcareous or black clay soils, local but sometimes locally plentiful and of weedy occurrence, known only from eastcentral Texas, from Dallas south to Austin, extending feebly southeast onto the Gulf Coastal Plain along the Trinity and Colorado Rivers; apparently isolated on the lower Rio Grande near Brownsville, Cameron County.—Map No. 160.—February to May.

Astragalus reflexus (reflexed, of the fruit) T. & G., Fl. N. Amer. 1: 334. 1838.—"Texas, Drummond!"Holotypus, Drummond 140, Collection II, NY (herb. Torr.)! isotypi, BM, G, GH, K ("Coll. III, in 1835"), OXF!—Tragacantha reflexa (T. & G.) O. Kze., Rev. Gen. 947. 1891. Hesperastragalus reflexus (T. & G.) Rydb. in Bull. Torr. Club 53: 165. 1926.

The Texas milk-vetch, A. reflexus, which must appear to the casual or uninstructed eye an inconsiderable and trifling weed, cannot fail to excite the admiration of anyone who has paused to ponder the mysterious impulses which have given rise to the protean variations on the astragaline motif. So far as I can see, no material advantage can have accrued to the species or to the individual plants, in the struggle for survival, through the modification of the tiny flower; and the remarkable, violet-purple, beaklike keel (reminiscent of Lupinus in outline, but lacking the function in pollenization by insects) which greatly surpasses the tiny, whitish wings and about equals the concolorous banner, seems to be the product of a sportive fancy operating outside the realm of common evolutionary pressures. Apart from the flower, the combination of scattered hirsute vesture, submembranous, retuse leaflets, and small, triquetrously compressed, sharply deflexed fruit combine to make A. reflexus instantly recognizable.

The Texas milk-vetch is apparently quite uncommon, and I have scanty data as to habits and ecology. Elihu Hall found it in "moist ground," which I have interpreted as temporarily wet bottomland rather than truly springy or boggy places; and Dr. Lloyd Shinners tells me (in correspondence) that it occurs in waste and weedy places in Hill and Dallas Counties. Gray described each locule of the pod as containing 3—4 ovules, but in all ovaries examined I have found only two or three pairs.