Astragalus flexuosus

  • Title

    Astragalus flexuosus

  • Authors

    Rupert C. Barneby

  • Scientific Name

    Astragalus flexuosus (Hook.) Douglas ex G.Don

  • Description

    38. Astragalus flexuosus

    Usually quite slender, sometimes tall, strigulose or villosulous with straight and appressed, incurved-ascending, or more rarely spreading hairs up to 0.2-0.6 (0.7) mm. long, the herbage greenish, cinereous, or silky-canescent, the leaflets bicolored, above yellowish-green and less densely pubescent or often glabrous; stems decumbent with ascending tips or weakly incurved-ascending to assurgent, (1) 1.5-6 dm. long, simple, slender, and subterranean for a space of 1-20 cm. (rarely exposed by erosion), commonly branched or spurred at the first aerial nodes, or at least from 1-several nodes preceding the first peduncle, often purplish at base, flexuous or zigzag distally; stipules (1) 1.5-7 mm. long, the lowest amplexicaul and connate into a campanulate, truncate or shortly bidentate, papery, brownish, purplish, or pallid sheath, the upper ones mostly longer, triangular to lance-acuminate, connate at base only or nearly free, the herbaceous blades commonly deflexed; leaves (1.5) 2-9 cm. long, the lowest shortly petioled, the upper ones subsessile, with (9) 11-25 linear, narrowly oblong, or oblong-oblanceolate, more rarely (in some lower, exceptionally all leaves) broadly oblong, obovate- cuneate, or obcordate, obtuse, truncate, or retuse, folded or sometimes flat leaflets (2) 3-19 mm. long; peduncles incurved-ascending or sometimes straight and divaricate, or erect, 1.5-13.5 cm. long, shorter or longer than the leaf; racemes loosely (7) 10-30-flowered, the axis elongating, (1) 2.5-13 cm. long in fruit; bracts submembranous, ovate or lance-acuminate, 0.6-4.5 mm. long; pedicels at anthesis 0.7-1.5 mm. long, in fruit becoming strongly arched outward, or geniculate at base and divaricate, somewhat thickened, 1.5-3.5 mm. long; bracteoles 0-2, minute when present; calyx 3.3-6 mm. long, strigulose-pilosulous with white, mixed black and white, or all black hairs, the subsymmetric or oblique disc 0.4-1 (1.3) mm. deep, the tube 2.4-4.2 mm. long, 1.8-2.9 mm. in diameter, the subulate or triangular-subulate teeth 0.5-2 mm. long; petals varying from whitish or creamy to lively purple, nearly always suffused distally with some shade of lilac; banner recurved through 45-90°, ovate-cuneate or rhombic-obovate, deeply or shallowly notched, 7.2-11 mm. long, 4.4-7.8 mm. wide; wings 6.9-10.5 mm. long, the claws (2) 2.4-4.2 mm., the narrowly oblong, oblong-elliptic or -oblanceolate, obtuse or emarginate, nearly straight or lunately incurved blades 5-7.9 mm. long, 1.7-2.9 mm. wide; keel 5-8.2 mm. long, the claws 2.2-3.9 mm., the half-obovate, obliquely obovate, or rarely half-circular blades 2.6-5.1 mm. long, 1.8-2.7 mm. wide, incurved through 90—120° to the bluntly or sharply deltoid, rarely minutely porrect apex; anthers 0.3-0.65 (0.8) mm. long; pod pendulous (from erect axes) or spreading (from horizontal axes), sessile or substipitate, the stipe up to 1.3 mm. long but commonly less, the body varying from linear-oblong or -oblanceolate to elliptic, oblong-, or ovate-elliptic in profile, (8) 11-24 mm. long, 2.7-9 mm. in diameter, either straight or gently in- or decurved, ± obcompressed and often shallowly sulcate dorsally (or when broad also ventrally), the thinly fleshy valves either green or mottled, becoming thinly to stiffly papery and brownish or stramineous, finely reticulate, thinly to densely strigulose, villosulous, or rarely glabrous; dehiscence apical and downward through the ventral suture, the valves gaping distally or somewhat twisted-recurved; ovules (12) 14—25; seeds pale or dark brown, olivaceous, or blackish, sometimes purple-speckled, pitted or nearly smooth 1.93 mm. long.

    The pliant milk-vetch, A. flexuosus, is a polymorphic aggregate of many small races minutely distinguishable from one another at the extreme point of their development, but fully intergradient and therefore not definable in mutually exclusive terms. During the preliminary studies I attempted to maintain A. gracilentus and A. Greenei together as a species coordinate with A. flexuosus and differing in the turgid or decidedly inflated pod of nearly always broader outline. But a full series of variants between the linear or linear-oblanceolate pod of A. flexuosus and the broader, plumper one of A. Greenei exists in nature. Jones considered his A. Diehlii as little more than "an extreme form of A. flexuosus," and the pod is scarcely distinguishable from that of some forms of "A. gracilentus’’ lately obtained in the type-region near Santa Fe. The old Phaca Fendleri and P. elongata, as well as Rydberg’s more modern Pisophaca ratonensis, P. sierrae-blancae, P. Saundersii, and P. stictocarpa, all fit readily into the present concept of A. flexuosus and are discussed below under the heading of minor variants.