Astragalus iodanthus

Low, diffuse, caulescent perennial, with a woody taproot and shortly forking or knotty caudex, more or less densely strigulose with straight, appressed or narrowly ascending, filiform (or largely shorter, flattened, somewhat scalelike) hairs up to 0.3-0.6 (0.7) mm. long, exceptionally villosulous with ascending and incurved or curly hairs, the herbage green or cinereous, the leaflets nearly always glabrous above; stems several, about 4-12 in mature plans, (3) 5-35 cm. long, prostrate or decumbent, simple or commonly spurred or shortly branched at 1-3 (5) nodes preceding the first peduncle, floriferous from below or above the middle, sometimes abruptly zigzag distally; stipules membranous or the uppermost thinly herbaceous, 2—6 mm. long, the lowest loosely imbricated or shortly discrete, semi- to almost fully amplexicaul, the median and upper ones progressively narrower, with triangular or lance-acuminate, rarely ovate, usually squarrose or deflexed blades; leaves (2) 3—7 cm. long, all petioled but the uppermost shortly so, with (7) 9—21 broadly obovate, oblong-obovate, or obovate-cuneate, rarely oblong- oblanceolate, elliptic, or suborbicular, mostly retuse or truncate, sometimes obtuse and mucronulate, flat or loosely folded leaflets (3) 5-15 (18) mm. long; peduncles ascending, sometimes at a wide angle, straight or incurved, (1) 2—4.5 cm. long, shorter than the leaf; racemes at first rather compact, early loosening, 7—17 (21)- flowered, the flowers at full anthesis widely ascending or spreading, declined thereafter, the axis (0.5) 1-4.5 (7.5) cm. long in fruit; bracts membranous, ovate, ovate-acuminate, or lanceolate, 1—3 mm. long; pedicels at first straight and ascending, at length arched out- or downward, at anthesis (0.3) 0.7-1.5 mm., in fruit thickened, (0.8) 1—2 mm. long, persistent; bracteoles usually 2, at base of calyx or just below it, minute or up to 1 mm. long, quite often 0; calyx 3.3-8 mm. long, thinly or densely strigulose (villosulous) with black or black and white hairs, the disc subsymmetric, the tube varying from shortly campanulate to subcylindric, the subulate teeth usually less than half as long as the tube, the whole becoming papery, marcescent, ruptured or not; petals purple, whitish with purple keel-tip, or all cream-colored; banner recurved through ± 45°, 9-15 mm. long, with either short- or long-cuneate claw and ovate, shallowly notched blade 5.3-8.5 mm. wide, wings either as long or decidedly shorter, the blades oblong-oblanceolate or linear-oblong, obtuse or truncate, nearly straight; keel nearly equaling to much shorter than the banner, the broadly lunate blades gently incurved through 45—55° to the very obtuse apex; anthers 0.45—0.65 (0.7) mm. long; pod essentially declined but often apparently spreading from humistrate peduncles or, when disturbed in pressing, deciduous from a minute boss on the receptacle, in outline very obliquely lanceolate, linear-lanceolate, or elliptic, 1.5-4 cm. long, (2.5) 3-8.5 mm. in diameter, commonly straight or a trifle arched downward in the lower half or third, then abruptly incurved through at least 90° and more commonly through 180° (and thus hamate), or sometimes more gently and yet further incurved so as to become annular or even coiled, either cuneate or long-acuminate into the ultimately obtuse base, acuminate distally into a laterally flattened, rigidly long-cuspidate beak, very variably compressed in 3 principal (but intergrading) modes: 1) strictly dorsiventral, with 2 nearly flat faces and narrow but obtuse lateral angles, the ventral face then low-carinate by the prominent suture; or 2) triquetrous, the lateral faces then either flat, low-convex, or slightly concave and the dorsal face widely and openly sulcate; or 3) compressed-triquetrous, the dorsal sulcus comparatively narrow; in any case the green, often red-mottled, somewhat fleshy, strigulose valves becoming stramineous or purplish, leathery or stiffly papery, cross-reticulate, either not inflexed or more often narrowly so, the septum 0.2-1.5 mm. wide, extending from base to below the middle of the pod, up to the middle, rarely up to the base of the unilocular beak; dehiscence apical, through the gaping beak, and often also tardily basal; ovules 14-30; seeds brown, purplish-brown, or almost black, smooth or rugulose-punctate, dull or lustrous, 2.2-3.5 mm. long.

When Watson described A. iodanthus, he interpreted it as closely related to A. Beckwithii and A. Parryi, and aligned it with these species in a loosely defined sect. Argophylli. This opinion of its affinities was accepted by Jones who (1923, p. 203) placed A. iodanthus next to A. cibarius in his expanded section of the same name; and later Rydberg (1929) based the heterogeneous Xylophacos sect. Iodanthi upon it. It has always been assumed that the pod of A. iodanthus is unilocular, an important generic character of Xylophacos, but at least two out of three examples of the fruit possess a perfectly normal, even though narrow, partial septum. One plant of this type (Stretch 265, NY) was referred by Rydberg to A. (Hamosa) drepanoloba (= our A. diaphanus), from which circumstance the epithet diaphanoides was chosen later for one variant of the species. Although the development of a septum is no longer regarded as of great phylogenetic significance, A. iodanthus is properly excluded from sect. Argophylli on other grounds. It has no close relative in that group as circumscribed in these pages, but it is not easy to exclude by technical characters. On the other hand, it is often difficult or even impossible to separate flowering material of its various forms from the polymorphic A. lentiginosus, from which it differs principally in a tendency to dorsiventral and triquetrous compression of the fruit, which is never inflated and commonly very strongly incurved. In A. lentiginosus there are many examples of little-inflated pods, some varieties being characterized by a fruit of this nature, while others put out occasional forms with narrow, clawlike pods quite similar to that of A. iodanthus, except that the section is subterete or didymous rather than triangular or transversely oblong. The pod of A. iodanthus is essentially deflexed, even though so greatly incurved as to bring its beak into an erect plane parallel with the raceme-axis, whereas in most forms of A. lentiginosus it is ascending or spreading. However in A. lentiginosus var. palans, the lance-ellipsoid, little-inflated pod varies from erect to decurved and its section varies from round to triangular, so that sometimes the only technical differential character that remains is the broader septum. The forms of A. lentiginosus most closely resembling A. iodanthus in habit, var. lentiginosus and var. platyphyllidius, produce now and again a phase remarkable for the so-called "carinate" flower, in which the petals are little- or poorly graduated and the keel becomes relatively broad and prominent. A flower of this sort is found frequently in A. iodanthus and is, in fact, characteristic of its var. vipereus.

In the original publication Watson mentioned a form of A. iodanthus, found near the Great Salt Lake in Utah, which differed from the Nevadan type in its more leathery, less incurved, incipiently septiferous pod. In reality this was the perfectly distinct species A. cibarius, superficially similar to A. iodanthus in habit of growth but differing importantly in its shortly stipitate, emmenoloboid fruit. In modern accounts of the genus, the two are traditionally associated but are not at all closely related. Now referred to sect. Malaci, A. cibarius has not been contrasted directly with A. iodanthus, but since they are still sometimes confounded and are likely to be so where their ranges overlap in eastern Nevada, the following key may be of practical value:

1. Pod truly sessile, deciduous from a conical receptacle and dehiscent on the ground, nearly always incurved or abruptly hooked through a half-circle or more; lower stipules small and inconspicuous; Nevada to s.-w. Idaho, s.-e. Oregon, and trans-montane California.......................................................... A. iodanthus

1. Pod contracted at base into a short, thick stipe (concealed by the marcescent calyx), dehiscent in situ or deciduous together with the pedicel, straight or gently incurved through ?-circle; lower stipules large, broad, ovate or obovate, obtuse and veiny, very conspicuous; Utah and e. Nevada to s.-e. Idaho, w. Montana, s. Wyoming, and w. Colorado............................................................................ A. cibarius

Like its relative A. lentiginosus, the present species is both polymorphic and variable, especially so in the form, size, and coloring of the flowers and in the curvature and compression of the fruit. Setting aside what seem to be trivial, however conspicuous minor variants, it is possible to distinguish one principal dichotomy within the species corresponding with geographic dispersal: