Slender, diffuse, perennial but sometimes flowering the first season and seldom long-enduring, strigulose nearly throughout with fine, straight, appressed or subappressed hairs up to 0.25-0.5 mm. long, the herbage cinereous or greenish-glaucescent beneath the vesture, the leaflets glabrous or nearly so and of a yellowish-green tint above; stems several or numerous from the root-crown or shortly forking caudex, decumbent or prostrate with ascending tips, (1.5) 2.5-30 (40) cm. long, commonly branched near the base and sometimes spurred at one or more nodes preceding the first peduncle, forming loosely woven mats; stipules submembranous or broadly membranous-margined, pallid or purplish, 2-5.5 mm. long, ovate- triangular or the upper ones lance-acuminate, about semiamplexicaul; leaves (2) 3-9 (11.5) cm. long, slender-petioled but the uppermost ones shortly so, with (7) 9-21 obovate, oblong-obovate, broadly oblanceolate, oval, or (especially in some lower leaves) oval-suborbicular, obtuse or emarginate, flat or loosely folded leaflets 2-12 (15) mm. long; peduncles slender, incurved-ascending at anthesis, recumbent in fruit, (3) 4-14 (15) cm. long, surpassing the leaf; racemes loosely (4) 6-20 (25)-flowered, the flowers ascending or spreading in age, the axis somewhat elongating, (1) 1.5-9 cm. long in fruit; bracts membranous, often purplish, triangular-ovate or lanceolate, 0.8-3 (3.5) mm. long; pedicels ascending, straight or nearly so, at anthesis slender, (0.5) 1—1.8 mm., in fruit a trifle thickened, 1.1-3.2 mm. long; bracteoles 0 (rarely a minute scale); calyx 5-7 mm. long, strigulose with white or mixed white and black hairs, the somewhat oblique disc 0.6-1.2 mm. deep, the membranous, often purplish tube 3.6-4.9 mm. long, 2.1-2.7 (2.9) mm. in diameter, the lance-subulate teeth 1.4—2.7 mm. long, the whole becoming papery, ruptured, persistent; petals pink-purple (drying bluish), the banner- and wing-tips often whitish; banner recurved through ± 45°, ovate- or obovate-cuneate, notched or subentire, 8.5-12 mm. long, 5-7.6 mm. wide; wings nearly as long as (rarely a trifle longer than) the banner, 8.6-11 mm. long, the claws 3.3-4.8 mm., the gently incurved blades 5.7-7.6 mm. long, either linear- oblong to oblanceolate and obtuse or truncate, or obliquely semiobovate and emarginate or shallowly bidentate, 1.7-3.6 mm. wide just below the apex; keel 6.5-8.4 mm. long, the claws 3.3-4.4 mm., the half-obovate blades 3.3-5 mm. long, 1.2-2.3 mm. wide, abruptly incurved through 85-95° and produced at apex into an erect or strongly porrect, narrowly triangular or subulate, acute, straight or slightly decurved beak 0.4—0.9 mm. long, the tip exceptionally unappendaged, bluntly deltoid; anthers (0.35) 0.5-0.65 (0.7) mm. long; pod ascending, sessile on the scarcely elevated receptacle, linear-lanceolate or linear in profile, slightly incurved, (1.3) 1.5-2.2 cm. long, 2.3-3.5 (4) mm. in diameter, rounded at base, contracted at apex into a very short, triangular, laterally compressed, cuspidate beak, otherwise compressed-triquetrous with acute ventral and obtuse lateral angles, the lateral faces flat or nearly so, the dorsal face narrowly sulcate, the green or purplish, thinly or quite densely strigulose valves becoming papery, stramineous or brownish, delicately cross-reticulate, inflexed as a complete or nearly complete septum 1—1.6 mm. wide; ovules (17) 18-26; seeds dark or chestnut-brown, sometimes purple-dotted, pitted or wrinkled but somewhat lustrous, 1.8-2.9 mm. long.—Collections: 60 (ii); representative: Jones 26,076, 26,083 (CAS, POM); Eastwood 8152, 16,972 (CAS); A. & R. Nelson 1443 (NY, SMU); McVaugh 8086 (SMU, TEX); Ripley & Barneby 11,199 (CAS, RSA); Hartman 622 (NY, US).
Open hillsides, valley floors, and sandy flats or stream beds, commonly among live oaks, about oak brush, or in juniper forest, sometimes in loose alluvium of washes or in disturbed soil along highways, without obvious rock preference, widespread, rather common and locally plentiful between 2700 and 6500 feet, (according to Kearney & Peebles as low as 1500 feet) over most of the upper Gila watershed in southeastern Arizona, southwestern New Mexico, northeastern Sonora, and south into the Mapimí drainage basin in northwestern Chihuahua.— Map No. 141.—(January) March to June, sometimes again after summer rains.
Astragalus nothoxys (falsely acute, the keel-petals supposedly simulating Oxytropis) Gray in Proc. Amer. Acad. 6: 232. 1864.—"Arizona, formerly the northern part of the Mexican province of Sonora, Prof. Thurber. San Luis Mountain and Guadeloupe Canon, Capt. E. K. Smith, in herb Torr."—Holotypus, collected by Thurber in 1851, NY! isotypus, GH (fragm.)! paratypi, GH (fragm.), NY!—Tragacantha nothoxys (Gray) O. Kze., Rev. Gen. 946. 1891. Oxytropis nothoxys (Gray) Jones in Proc. Calif. Acad. Sci. II, 5. 677. 1895. Spiesia nothoxys (Gray) Jones, l.c., nom. provis. Aragallus nothoxys (Gray) A. Hell., Cat. N. Amer. Pl. 4. 1898. Hamosa nothoxys (Gray) Rydb. in Bull. Torr. Club 54: 330. 1927.
Astragalus madrensis (of Sierra Madre Occidental) Jones, Rev. .Astrag. 274, Pl. 69. 1923. —"Rather common in the Sierra Madres of Chihuahua Mexico, San Diego Cañon, Colonia Juarez, and Sabinal, Jones."—Lectotypus, collected in San Diego Canyon, Sept. 16, 1903, M. E. Jones, POM (2 sheets)! paratypus (from Colonia Juarez, Sept. 11, 1903, Jones), POM! —Hamosa madrensis (Jones) Rydb. in N. Amer. Fl. 24: 426. 1929.
Hamosa Gooddingii (Leslie Newton Goodding, 1880- ) Rydb. in Bull. Torr. Club 54 : 20. 1927.—"Type collected on rocky slope in the Huachuca Mountains, Arizona, May, 1912, L. N. Goodding 1299 ... "—Holotypus, NY!—Astragalus Gooddingii (Rydb.) Tidest. in Proc. Biol. Soc. Wash. 48 : 40. 1935 & op. cit. 50: 21. 1937.
The beaked milk-vetch, A. nothoxys, might be taken as the prototype of its section, of which it has the characteristic narrowly oblong, linear, or linear-lanceolate, compressed-triquetrous, fully bilocular pod with a groove along the narrowest of the three faces opposed to the prominent but slender ventral suture. Among the perennial or potentially perennial species it may be recognized by its small leaflets of a pale subglaucescent green color, by the comparatively many, loosely racemose, pinkish-purple flowers, and by the ordinarily triangular-acuminate keel-tip. The latter varies from narrowly triangular and erect in a line with the outer curve of the keel-blade into a subulate-attenuate, outwardly arcuate (and thus porrect), cusplike appendage, and from nearly 1 mm. in length to a minute, rarely obsolete process. Whatever its shape, the cusp arises laterally, from the functional apex of the oblique petal, not terminally as in Oxytropis, with which A. nothoxys has been often but irrelevantly compared. In the type-collection of Hamosa Gooddingii, one plant, as described by Rydberg, has beakless keel-petals; another, mounted with it and otherwise indistinguishable, is normal A. nothoxys. The original description of A. madrensis, maintained by Rydberg as a species of Hamosa sect. Tricarinatae, is faulty in several respects, particularly in regard to the "reflexed" flowers and "deltoid and obtuse" keel-tip. The material from which the description was drawn consists of several plants collected in September; they are in a stage of renewed growth after autumnal rains, with tender new foliage starting from the middle and summit of indurated but formerly herbaceous stems, and thus they have a somewhat abnormal appearance. The best of these, from San Diego Canyon, has been chosen as lectotypus. It is the only one with flowers (about 2), which are clearly ascending from straight, erect pedicels, and the keel has the mucroniform appendage proper to A. nothoxys. The plants from Colonia Juarez should perhaps be considered cotypical, for they alone have good fruits, although these have already fallen and were probably picked off the ground, already dehiscent. The collection from Sabinal, although a mere fragment, is probably conspecific. Rydberg’s description of the pod as "strongly reflexed" is impossible to reconcile with the stiffly erect fruiting pedicels of Jones’s plant, and Hamosa madrensis seems to be a figment of the imagination. The Texan record of A. madrensis (Rydberg, l.c.) was based on a poor flowering specimen of A. allochrous collected near Fronteras by Bigelow (Mex. Bound. Surv. No. 261, NY).
In the live oak woodlands of southeastern Arizona A. nothoxys is locally abundant, especially on caliche soils. Like many plants injurious to man’s interests, it flourishes in disturbed environments. On overgrazed and unwisely managed cattle ranges, it is often a serious pest, being one of the most greatly feared locoweeds of the region.