Astragalus sinaloae

  • Title

    Astragalus sinaloae

  • Author(s)

    Rupert C. Barneby

  • Scientific Name

    Astragalus sinaloae Barneby

  • Description

    125. Astragalus sinaloae

    Slender, surely perennial but the root and caudex not seen, minutely strigulose with appressed hairs up to 0.15-0.2 mm. long, the herbage green, the leaflets glabrous above; stems decumbent, ± 3-4 dm. long, branched at 2-4 nodes preceding the first peduncle; stipules 1.2-2.5 mm. long, semiamplexicaul, the triangular-subulate blades reflexed; leaves 2-5 cm. long, the lowest shortly petioled, the rest subsessile, with 13-17 oblong-obovate or -elliptic, retuse, flat leaflets 3-8 mm. long; peduncles incurved-ascending, (2) 4-6 cm. long; racemes rather densely 15-33-flowered, the flowers (sometimes fewer on depauperate, lateral branchlets) early declined, the axis somewhat elongating, 2-5 cm. long in fruit; bracts membranous, triangular-subulate, ± 1 mm. long; pedicels at anthesis 0.5-0.8 mm. long, early arched out- and downward, in fruit thickened, 1.3-1.6 mm. long, apparently persistent; bracteoles 0; calyx 2.6-2.7 mm. long, minutely white-puberulent, the subsymmetric disc 0.4-0.5 mm. deep, the tube 1.8-2 mm. long, 1.8-2 mm. in diameter, the triangular-subulate teeth 0.7-0.8 mm. long, the whole becoming papery, marcescent unruptured; petals "white," drying yellowish, of nearly equal length; banner recurved through ± 40°, obovate-spatulate, shallowly notched, ± 5.3 mm. long, 3.3 mm. wide; wings 4.9-5.2 mm. long, the claws 2.1-2.2 mm., the lanceolate blades ±3.5 mm. long, 1.4 mm. wide, rather abruptly incurved in the distal half; keel 5.3 mm. long, the claws 2.3 mm., the half-elliptic blades 3.3 mm. long, 1.9 mm. wide, incurved through 95° to the rather sharply deltoid apex; anthers 0.3-0.45 mm. long; pod reflexed, very shortly stipitate, the stipe 0.6-0.8 mm. long, concealed by the calyx, the body linear-acuminate in profile, lunately incurved, 1.2-1.4 cm. long, 2.2-2.5 mm. in diameter, cuneate at both ends, cuspidate at apex (the cusp ± 1 mm. long), compressed-triquetrous, carinate ventrally by the suture, grooved dorsally, the lateral faces nearly flat, the lateral angles narrow but obtuse, the thin, very sparsely white-strigulose valves becoming papery, stramineous, prominently reticulate, inflexed as a complete septum ±1.5 mm. wide; dehiscence and seeds unknown; ovules 10-12.—Collections: typus only.

    Open rolling valley in pine forest, 6000—7000 feet, in argillaceous soils, known only from the type-locality in the Sierra Surotato, Sinaloa.—Map No. 51.—August and September.

    Astragalus sinaloae (of Sinaloa), sp. nov., A. ervoideo H. & A. ut videtur affinis, floribus paullo minoribus, petalis subaequilongis, et legumine puberulo ab eo facile distin- guenda.—Herba perennis, parce strigulosa; stipulae liberae; foliola 13-17 oblonga; racemi densiuscule 15-33-flori; calyx campanulatus ± 2.6 mm. longus, dentibus tubo subdimidio brevioribus, petala alba subaequilonga, 4.9-5.3 mm. longa; legumen brevissime stipitatum renexum lineari-acuminatum incurvum ±1.3 cm. longum triquetrim compressum dorso sulcatum biloculare puberulum.—Sinaloa: Sierra Surotato, September 1-10, 1941, Howard Scott Gentry 6283.—Holotypus, MICH! isotypi, DS, GH, NY!

    The type-collection of A. sinaloae was distributed under the name of A. vaccarum, a species like it in the tiny, declined flowers and the narrow, hamosoid pod which is, however, truly sessile and deciduous from the receptacle and not stipitate and persistent as in sect. Miselli. The nearest ally of A. sinaloae is A. ervoides, the pod of which is quite similar in structure but glabrous. The flowers of these two species are similar in most fine details, although the slightly shorter petals of the Sinaloa milk-vetch are all of about the same length, giving a peculiar blunt look to the corolla as viewed in profile. The calyx of var. Maysillesii, the form of A. ervoides geographically nearest to A. sinaloae, is two or three times as long, its teeth nearly four times longer.

    A specimen of doubtful identity, but evidently representing a close relative or possibly a variant of A. sinaloae, has been collected at about 1900 feet in Municipio de Concordia, near Pánuco, Sinaloa (M. P. Dehesa 1585, US). The plant differs from A. sinaloae as described above in its larger leaflets, looser racemes, slightly shorter, broadly deltoid calyx-teeth, and slightly longer petals, but especially in the glabrous ovary and forming pod. If the description of A. sinaloae were expanded to include this form, the species could still be distinguished from A. ervoides by its petals of subequal length.