Astragalus tephrodes

Low but sometimes quite coarse, loosely or densely tufted perennials, acaulescent or shortly caulescent, the caudex ultimately branching but scarcely lignescent, the vesture of the whole plant extremely variable both in density and orientation of the hairs, the herbage strigulose, pilosulous, or villosulous with straight and appressed, straight and largely or partly ascending, incurved and ascending, or sometimes largely or exclusively loose and sinuous hairs up to 0.4-0.9 (1) mm. long, either green, or greenish-cinereous, or silky-canescent, the leaflets either equally pubescent on both sides or medially glabrescent to glabrous above, the upper surface commonly brighter green (even beneath the vesture) than the lower; stems several, 0-15 cm. long, prostrate when developed, the internodes either all concealed by stipules, or a few produced and up to 2 (2.5) cm. long, the whole stem in any case shorter than the longest leaves and inflorescences; stipules submembranous becoming papery-scarious and pallid, deltoid, ovate-acuminate, lance-acuminate, or -caudate, 2—15 mm. long, decurrent around ½ or more of the stem’s circumference, very exceptionally a few of the lowest pairs fully amplexicaul and obscurely connate, all thinly to densely pubescent dorsally, rarely subglabrous; leaves 3-24 cm. long, all petioled, with 11-31 broadly oblanceolate, obovate, oval, rhombic-ovate, -elliptic, or rarely suborbicular, obtuse, acute, or rarely emarginate, flat or loosely folded leaflets 2-27 mm. long, the midrib sometimes prominent beneath; peduncles stout or quite slender, 4-40 cm. long, either longer or shorter than the leaf, commonly incurved-ascending but sometimes erect at anthesis, either arcuate-procumbent or prostrate and radiating in fruit; racemes loosely (9) 10-26 (35)-flowered, the axis somewhat or scarcely elongating, 2-20 cm. long in fruit; bracts membranous becoming scarious, lanceolate or ovate-acuminate, 1.5-11 mm. long; pedicels ascending or a trifle arched outward, at anthesis slender, 0.6—2.2 mm., in fruit thickened, 1.2—3.4 mm. long, bracteoles usually 0, if present very rarely conspicuous; calyx (5) 6-14 mm. long, loosely strigulose, pilosulous, or rarely villous, with white or mixed white and black, subappressed, ascending, or loosely spreading, straight or sinuous hairs up to 0.4-0.85 (1.1) mm. long, the oblique disc 1-2.8 mm. deep, the cylindric to deeply campanulate, pallid or often purplish tube (3.5) 4.5-10.2 mm. long, 3.2-5.2 mm. in diameter, the subulate or triangular-subulate teeth 1.2-3.8 mm long, the ventral pair often broadest and sometimes longest, the whole becoming papery, ruptured, marcescent; petals pink-purple to dull lilac, sometimes dirt; white but the banner then margined and the keel tipped with some shade of dull or lively purple, the anthocyanin turning bluish when first dried, fugacious with time; banner gently recurved through ± 45° (or further in withering), obovate cuneate, broadly oblanceolate, rhombic-elliptic, or spatulate, shallowly notched to subentire, 11.5—24 mm. long, 6.7—12.3 mm. wide; wings a trifle shorter to a trifle longer than the banner, (10.8) 11.8—22.7 mm. long, the claws (4) 4.2—13.5 mm., the lance-oblong or narrowly oblong, obtuse, nearly straight blades (7.2) 8.1-12.3 mm. long, 2.3-3.7 mm. wide; keel (9.2) 10.2-20.1 mm. long, the claws (4.2) 4.5-13.5 mm., the half-obovate or lunately elliptic blades (5.6) 6.48.8 mm. long, (2.5) 2.9-4 mm. wide, gently and evenly or sometimes abruptly incurved through 80—95° to the blunt apex; anthers 0.5—0.85 (0.9) mm. long; pod ascending (humistrate), obliquely lance-ellipsoid, oblong- or ovoid-ellipsoid more rarely ovoid-acuminate, 1.3—4 cm. long, 5—16 mm. in diameter, lunately incurved its whole length or straight proximally and only the beak incurved, rounded or truncate at base, contracted distally into a deltoid, triangular, or lance-acuminate, cuspidate, laterally compressed beak 3—10 mm. long, elsewhere strongly obcompressed, flattened or low-convex dorsally, carinate ventrally by the thick, obtuse prominent but often depressed suture, the dorsal suture also salient but narrower than the ventral one and commonly undulate, the thinly to quite thickly fleshy green or purplish, densely to quite thinly strigulose-pilosulous or rarely glabrous valves becoming stramineous or brownish, thinly leathery to stiffly woody, transversely reticulate or rugulose, when fleshy also longitudinally wrinkled, not inflexed, or if so the septum very narrow and obscure, not over 1 mm. wide; dehiscence apical, after falling, the beak gaping, the exocarpic sutures splitting lengthwise in age; ovules 24-45; seeds brown or black, smooth, pitted, or somewhat wrinkled, dull or moderately lustrous, 1.8-3.6 mm. long.

The taxonomic complexity of A. tephrodes, sens. lat., was discussed at length in a preliminary revision (Barneby, 1947, pp. 463—471), and it only remains to add that subsequent field experience has done little to clarify the racial situation within the species. Any hope that the pubescence-phases of var. brachylobus might be more exactly defined by means of ecological correlation has proved groundless, and the reduction of A. remulcus, A. pephragmenus and Xylophacos lenophyllus to one polymorphic variety was fully justified. In most given populations of var. brachylobus the individual members are rather uniform in vesture, but some show marked variation. On the north slope of Pinal Mountain in Gila County, Arizona, strigulose-cinereous plants closely resembling the typus of var. brachylobus have been seen growing promiscuously with silvery-hirsute plants apparently identical with the typus of A. pephragmenus, a species which originated on the "crest of the Pinals." Thinly strigulose, finely villosulous, and densely silvery-pilose states of var. brachlobus have been collected in identical environments in yellow pine forest, sometimes only a few miles apart. The whole species seems to be genetically unstable in this respect.

As more and more material of A. tephrodes has been studied, a picture has been built up of an almost uninterrupted clinal series of slight modifications extending spatially, in approximately linear sequence, across Arizona to extreme southern Utah, southern Nevada, and adjoining California. The smallest flowers and the smallest pods of thinnest texture are found at or near the southeastern limit of the species-range, the longest flowers and largest, most fleshy pods at somewhat isolated points to the northwest. An attempt to organize this series by fragmentation into subsidiary groups is bound to be somewhat arbitrary, and the varieties defined below should be understood as points on a sliding scale or as nominal foci about which like forms can advantageously be brought together for purposes of classification. There can be very little question that the type-populations of var. tephrodes and var. eurylobus, which differ from each other so greatly and in so many features, are genetically distinct, and the aims of taxonomy would be defeated if they were united under one name. However, as soon as the small-flowered var. tephrodes is detached from the body of the species, logic demands equal treatment for the robust extremes which have differentiated out at the opposite end of the series. For this reason var. brachylobus of my earlier revision is here further broken up into three coordinate varieties. The following key does not pretend to account for states intermediate between the foci of variation.