Astragalus callithrix

  • Title

    Astragalus callithrix

  • Author(s)

    Rupert C. Barneby

  • Scientific Name

    Astragalus callithrix Barneby

  • Description

    196. Astragalus callithrix

    Shortly caulescent or subacaulescent, loosely tufted, perennial but of short duration and flowering the first season, the stems and herbage densely white-pilose with straight and narrowly ascending, together with somewhat curly and subappressed hairs up to 1—1.5 mm. long; stems few or sometimes solitary, prostrate or ascending from the root-crown or from a shortly forking caudex, 1-6 (exceptionally, in shelter of sagebrush, up to 15) cm. long, branched or spurred at or below the middle, the internodes either developed and up to 1 (3.5) cm. long, or all contracted and concealed by stipules; stipules submembranous, ovate or triangular-acuminate, 2-5 mm. long, erect, pilose dorsally, semiamplexicaul; leaves 2-8 (14) cm. long, with flaccid, deciduous petiole and (7) 9-19 (21) obovate, obovate-cuneate, suborbicular, or rarely broadly lanceolate, obtuse or truncate- emarginate, flat or loosely folded, thick-textured leaflets 2-13 mm. long; peduncles (1) 2-5 (13) cm. long, shorter than the leaf, at first anthesis erect or arcuate- ascending, spreading or procumbent in fruit; racemes loosely but sometimes sub- capitately 5-15-flowered, the axis scarcely elongating, 0.5-4 (8) cm. long in fruit; bracts membranous with firm midrib, lanceolate or lance-acuminate, 3-7.5 mm. long; pedicels at anthesis slender, 1—1.5 mm. long, in fruit thickened but scarcely or not elongating, ascending or arched outward; bracteoles 0-2, minute when present; calyx 6.8-13.3 mm. long, the obliquely turbinate disc 0.9-1.8 mm. deep, the membranous, purplish, cylindric tube 5.5-10.8 mm. long, 2.7—4 mm. in diameter, the subulate or lanceolate teeth 1-3.2 mm. long, the dorsal one sometimes shortest, the ventral sinus deely cut back, the orifice oblique; petals bright pink-purple; banner recurved through ± 40°, oblanceolate or rhombic- oblanceolate, emarginate, 16-26 mm. long, 6-11 mm. wide; wings 15.3-23.8 mm. long, the claws 6-11 mm., the linear-oblong or -lanceolate, obtuse, nearly straight blades 10-14.5 mm. long, 2-2.8 mm. wide; keel (12) 13-20.7 mm. long, the claws 6.8-11.5 mm., the lunately half-elliptic blades 7-10 mm. long, 2.8-3.4 mm. wide, gently incurved through ± 45° to the broadly rounded apex; anthers 0.5-0.7 mm. long; pod ascending or loosely spreading (commonly humistrate), obliquely oblong-ovoid, 1-1.6 (2) cm. long, 5-7.5 mm. in diameter, slightly tumid, truncate or rounded at base, in the lower ? straight, strongly obcompressed, and dorsally flattened or openly sulcate, passing upward and incurved through 90-180° into a deltoid or triangular-acuminate, sharply cuspidate, laterally compressed beak, the somewhat fleshy, green valves hirsute (but not so densely as to conceal either the shape or surface of the pod) with fine, lustrous, widely spreading, straight or somewhat twisted hairs up to 2-2.5 mm. long, becoming stramineous, smooth or a trifle rugulose, not inflexed; dehiscence apical, through the gaping beak, after falling; ovules 24-34 (37); seeds ocher-brown, smooth or nearly so, ± 2 mm. long.—Collections: 4 (ii); representative: Magurie & Holmgren 25,139 (CAS, MO, NY, RSA, TEX, WS); Ripley & Barneby 4434 (CAS, GH, RSA); Raven 13,533 (NY).

    Bare open places on semistabilized dunes or in deep sandy soil on the floor of sagebrush valleys, 5100-5200 feet, locally plentiful but apparently rare and highly localized, known only from a small area lying between the Quinn Canyon and Hot Creek Ranges in northeastern Nye County, Nevada.—Map No. 80. May and June.

    Astragalus callithrix (with beautiful hair) Barneby in Leafl. West. Bot. 3: 103, Pl. opp. p. 108, fig. C. 1942.—"Nevada: ...seven miles south of Callaway, northeast Nye Co., altitude 5150 ft., 26 May 1941,.. Ripley & Barneby No. 3531."—Holotypus, CAS! isotypus, RSA!

    This decorative, dwarf, large-flowered astragalus is related to A. marianus and probably represents a recently specialized derivative which has become adapted to a dune habitat. As shown on the map of dispersal, the ranges of A. marianus and A. callithrix are contiguous but not overlapping, and their ecological requirements are so different that they could not become closely sympatric. To the differential characters already brought out in the subsectional key, I should add that the racemes of A. callithrix are on the average more numerously flowered and tend to become both longer and looser in fruit, while the petals (so far as observed when fresh) are much more richly colored. In the original publication A. callithrix was compared with A. utahensis and A. nudisiliquus. The latter is similar in so far that the pod is only thinly hirsute and not at the same time tomentose, but A. callithrix lacks the fine cottony pubescence which is characteristic of subsect. Eriocarpi, and I can no longer see any suggestion of close kinship in that direction.

    The Callaway milk-vetch, A. callithrix, is known at present from only two valleys in northeastern Nye County, these parallel but separated by the low volcanic Pancake Range. In the more western valley, where the species is abundant over a considerable area to the north and northeast of Warm Springs, the flowers are much larger than found in the type-station (calyx ± 10-13, not ± 7 mm., banner 22.5-26, not ± 17 mm. long) and the ovules are more numerous (29-37, not 24—26). Evidently two populations exist, effectively restricted to their islands of sandy soil within an oceanic waste of undifferentiated sagebrush. The evaluation of these variants must await a more thorough scrutiny of the region, for other populations with flowers of intermediate size may exist.