Astragalus adsurgens

Commonly rather coarse but sometimes low, caulescent perennials, with a tough, woody taproot and knotty or shortly forking caudex, densely to quite thinly strigulose with fine, straight, appressed, dolabriform hairs up to (0.35) 0.55-1 mm. long, the herbage silvery-silky, greenish-cinereous, or green, the leaflets varying from densely pubescent to glabrous above; stems several or numerous, (0.2) 0.5-3 dm. long, ascending from the decumbent base or less often erect, commonly simple or simple except for 1-2 spurs arising from axils immediately preceding the first peduncle (the spurs rarely produced into floriferous branches),angular-striate, often zigzag distally, together forming low tufts or clumps of rounded outline; stipules 4-13 (16) mm. long, papery-scarious and pallid or early becoming so, briefly adnate to and sometimes also behind the petiole-base, amplexicaul and connate through ? or more of their length into a loosely or tightly clasping sheath, this becoming fragile and sometimes ruptured in age, the upper ones with triangular, lanceolate, or lance-acuminate, mostly erect blades; leaves 4-17 cm. long, the lower petioled, the upper more shortly so or subsessile, with (7) 11-25 oblong, linear-oblong, narrowly to broadly elliptic, lanceolate, or oval, obtuse, subacute, or rarely subretuse, flat or marginally elevated, often dorsally carinate leaflets (4) 8-27 (33) mm. long, the upper surface either smooth or pinnately veined; peduncles mostly stout, erect or incurved-ascending, ribbed, (3) 4-14 (17) cm. long, about equaling or well surpassing the leaf; racemes densely (7) 10-50-flowered, the narrowly ascending flowers imbricated in obovoid, subcapitate heads or cylindro-oblong spikes, the axis little elongating after anthesis, (0.6) 1-9 (13) cm. long in fruit; bracts membranous or subherbaceous distally, lanceolate or lance-acuminate, 2-8 mm. long; pedicels erect, at anthesis subobsolete or up to 0.5 (0.8) mm. long, in fruit a trifle thickened or clavate, up to 0.4-1 mm. long; bracteoles 0; calyx 4.8-10.5 mm. long, densely strigulose with mixed black and white, more rarely all white or all black, straight or sometimes crisped hairs, the disc 0.5-1.4 mm. deep, the cylindric or campanulate tube 3-7 mm. long, 2-3.2 mm. in diameter, often a little distended dorsally above the obliquely obconic base, the linear, subulate, or subulate-setaceous, erect or arcuately spreading teeth 0.6-4.2 mm. long, the whole becoming papery, ruptured, marcescent; petals variable in color, magenta-purple, reddish-lilac, dull slate-blue, pale milky-white (the keel then often deeply maculate), or whitish drying cream-color, all withering-persistent; banner nearly erect or gently recurved through ± 25°, oblanceolate, rhombic-oblanceolate, or spatulate, notched or rarely subentire at apex, 11-19.5 mm. long, 4-7 (9) mm. wide; wings 9.7-17.5 mm. long, the claws 4.1-8.3 mm., the narrowly oblong, linear-oblong, or oblong-oblanceolate, obtuse, obliquely truncate, or obliquely notched, straight or nearly straight blades (5.2) 5.8-10 mm. long, 1.3-2.5 mm. wide; keel 8-15 mm. long, the claws 3.8-8.3 mm., the half-elliptic or obliquely elliptic blades 4.2-7 mm. long, 1.7-2.7 mm. wide, incurved through 50—90° to the blunt or sometimes sharply deltoid apex; anthers 0.5-0.8 mm. long; pod erect, sessile or shortly stipitate, the stipe when present up to 1.8 mm. long but concealed by the calyx, the body narrowly ovoid-, oblong-, or lance-ellipsoid, 5.5-12 mm. long, 2.3—4 mm. in diameter, straight or a trifle incurved, rounded or cuneate-obconic at base, contracted at apex into an erect or somewhat declined, cusplike beak 0.7-2.5 mm. long, triquetrously compressed with acute ventral and narrow but obtuse lateral angles, the lateral faces flat or low-convex, the dorsal face narrower, openly but often deeply sulcate, the thin, green, at length smooth, papery, stramineous valves densely strigulose with short, sinuous, and often some longer, straighter, mixed black and white or all white hairs, inflexed as a complete or almost complete septum 0.7—1.5 mm. wide; dehiscence ultimately through both sutures and the septum, the valves tending to twist outward; seeds dusky-olivaceous, dark brown, or nearly black, smooth but dull, 1.5—2.6 mm. long.

The standing milk-vetch, A. adsurgens, is easily recognized in our flora by the combined features of a determinate root-crown at soil-level, dolabriform pubescence, connate stipules which early become pallid and scarious, and narrowly ascending flowers crowded into headlike or spikelike racemes and giving rise to small, erect, trigonous pods invested by the marcescent petals and calyx. In the fruiting stage it is sometimes confused with low forms of A. canadensis, similar in the type of vesture and connate stipules; but the flowers of the Canada milk-vetch are reflexed when fully open, the stems arise from slender subterranean surculi, and the pod is broader terete or less sharply three-angled, and of much thicker texture. The standing milk-vetch is sympatric over a great part of its American range with A. agrestis, a species similar in the connate stipules and crowded inflorescence of ascending flowers, but quickly distinguished by its basifixed hairs, subterranean points of renewal, and shorter, broader pod hirsute with long, white hairs. .

As early as 1831 Hooker (Fl. Bor.-Amer. 1: 149) expressed the opinion that the American astragalus that has passed in the twentieth century under the names A. nitidus or A. striatus was conspecific with the Siberian A. adsurgens Pall., and Gray upheld Hooker’s judgment in 1864. There can be no question of the close kinship between the species of Pallas and our A. striatus. The habit of growth, the leaves and stipules, the shape and color of the petals, the form of the pod, and even the ovule number are all essentially the same in both. The flowers of A. adsurgens in Asia vary considerably in size and coloring, in very much the way that those of A. striatus vary in America, and segregates based on these variations in combination with slight alterations in the calyx have been proposed on both sides of the Pacific. I have not seen enough material from the whole Asiatic range to evaluate a racial situation involving such local geographic variants as A. marinus Boriss.; but there is sufficient material from Russia in this country (NY, US) to show that A. adsurgens and A. austrosibiricus B. Schischk., as defined in Flora U. R. S. S., are morphologically confluent in the same way that our A. striatus, A. Chandonetii, and A. sulphurescens run together into an indivisible complex. Peter-Stibal (1937, p. 63), faced with the same problem, concluded that there was but one variable species in the Chinese flora. Considered collectively the Asiatic forms of A. adsurgens differ from ours in the relative proportions of the calyx and banner. In the Old World plant the tube of the calyx is comparatively short, so that the claws of the wings and keel are further exserted than in the New World plant, and the aspect of the flower as seen in profile is perceptibly different. No other consistent differential character seems to exist. In America the lateral and dorsal sinuses between the calyx-teeth tend to be narrow and subacute, whereas in Asia they are commonly all wide and obtuse, the teeth being less crowded together toward the calyx’s abaxial side. These are hardly characters of specific value, and a return to Hooker’s concept of an amphi-Pacific A. adsurgens can no longer be avoided.

The following key is designed for use in America only; the var. adsurgens is extremely polymorphic and may well cover several geographic races deserving coordinate status.