Astragalus praelongus

Title

Astragalus praelongus

Authors

Rupert C. Barneby

Scientific Name

Astragalus praelongus E.Sheld.

Description

184. Astragalus praelongus

Coarse and ordinarily tall, either nearly glabrous, or the upper stems, lower surface of the leaflets, and the inflorescence thinly strigulose with straight, appressed hairs up to 0.3-0.65 (1) mm. long, the thick-textured herbage either green or pallidly glaucescent; stems several, erect and ascending in clumps from an at length shortly forking, indurated base, (1.5) 2-6 (8) dm. long, simple or bearing short spurs or branchlets near the base (and sometimes also inserted between peduncle and petiole distally); stipules thinly herbaceous becoming papery- scarious, 2.5-7 (9) mm. long, the lowest often broader than long, the upper ones commonly deltoid and reflexed, all ± decurrent around 1/3-3/4 the stem’s circumference; leaves 4—18 (22) cm. long, all petioled or the uppermost subsessile, with (7) 11-27 (33) obovate, oblong-obovate, lanceolate, or oblanceolate, obtuse or retuse, or in some upper (all) leaves elliptic and acute leaflets (3) 8-35 (50) mm. long; peduncles stout, erect, 6-26 cm. lone- racemes 10-25 (33) -flowered, rather dense at early anthesis, the reflexed flowers then retrorsely imbricated, becoming looser, the axis 3.5-13 (16) cm. long in fruit; bracts membranous, ovate or lanceolate, 1.5-5 (12) mm. long; pedicels at anthesis ascending or a trifle arched outward, (1) 1.5-3 mm. long, in fruit ascending, straight, clavately thickened, (3.5) 4-7 mm. long; bracteoles 2, minute, or lanceolate and up to 3.5 mm. long; calyx 5.8-13 (14) mm. long, glabrous or thinly strigulose with black or white hairs 0.05-0.5 (0.75) mm. long, the strongly oblique, fleshy disc 0.9-1.7 (2) mm. deep, the tube 4.4-6.5 (7.5) mm. long, 3.5-5.4 (6) mm. in diameter, dorsally gibbous at base, the lance-subulate to broadly deltoid teeth 0.3-5.5(6.6) mm. long, all erect, or the lateral and dorsal ones rarely a little recurved in age; petals ochroleucous with faintly maculate keel-tip, exceptionally pink-tinged; banner recurved through 45° (often further in withering), 15-23.5 mm. long, the broad claw expanded into an oval or rhombic-ovate, notched, somewhat fleshy blade 7.8-12 mm. wide, wings 15-22 mm. long, the claws 5.3-8.4 mm., the narrowly oblong-oblanceolate, little incurved, obtuse but often obscurely erose-emarginate blades 10-15.7 mm. long, 2.5-4.5 mm. wide; keel 11.5-17 mm. long, the claws 5.1-8.6 mm., the half-obovate blades 6.8-9 (10) mm. long, 3.6-4 7 mm. wide, abruptly incurved through 90-105° to the bluntly rectangular apex; anthers (0.7) 0.8-1 (1.2) mm. long; pod erect, horizontally spreading, or more rarely declined sessile, subsessile, or stipitate, the turgid or decidedly inflated (but never bladdery) body varying from narrowly ellipsoid to broadly ovoid, obovoid or subglobose, 1.8-3.8 (4.2) cm. long, 0.5-1.5 cm. in diameter, cuspidate at apex, straight or a little incurved, subterete or somewhat dorsiventrally compressed, carinate ventrally by the very thick, prominent suture, rounded or shallowly sulcate dorsally, the thickly fleshy, green or purplish-speckled valves becoming stiffly leathery or subligneous, rugulose and brown or stramineous, pulpy-filamentous within, externally glabrous, minutely scaly-puberulent, or strigulose with white hairs up to 0.05—0.3 mm. long, inflexed as a narrow partial septum 0.8-2.3 mm. wide; ovules (40) 44-75 (84); seeds brown, sometimes purple-speckled smooth but dull, 3-3.8 mm. long.

The stinking milk-vetch, A. praelongus, is a coarse, rather handsome astragalus, distinguished from all but its close relative A. Pattersoni (keyed above) by its truly or apparently hairless foliage of thick texture, dense racemes of rather large, nodding, ochroleucous flowers, basally pouched calyx of the same color as the petals, and large, internally pulpy, partially bilocular pods. The freshly gathered herbage gives forth a strong (to some people nauseating) smell of selenium, which seems to gather strength during the long process of drying out herbarium specimens. The plants are highly toxic but are seldom browsed by healthy animals, and then only as a last resource, even though, being remarkably drought-resistant, they form tufts of apparently appetizing greenery in a landscape turned brown and sere from lack of rain. The forming fruits are commonly infested with maggots, so that despite the large number of ovules, comparatively few ripen into viable seeds. The species, nevertheless, is a vigorous and successful one, flourishing in areas subject to rapid erosion and hostile to much plant life. The typical form of A. praelongus is reportedly used by the Hopi Indians, under the name of  sisikinga, in treatment of bladder troubles.

The foregoing description of A. praelongus acknowledges a relatively enormous range of variation in stature of the plants, in width and outline of the leaflets, in length of the calyx- teeth, and (to less degree) in length of the petals, but the various types of variation are only feebly correlated among themselves and hardly at all with rational patterns of dispersal. This general statement must be modified to the extent that the tallest stems, the widest (often emarginate) leaflets, and the shortest calyx-teeth are found most frequently, though only rarely all together, toward the west edge of the species-range. Variation in the pod is very marked and has been the basis for the elaborate segregation of minor variants in the rank of species. The largest pods, of thickest texture, commonly truncate or nearly so at base, are found chiefly in Arizona’s northern tier of counties and in the Muddy and Virgin Valleys in southwestern Utah and southern Nevada. Such fruits may be either glabrous or puberulent;  when exceptionally thick-walled and succulent, they tend to spread horizontally from the raceme-axis or eventually nod, apparently of their own weight. A fruit of this type characterized the original A. praelongus and the negligible Jonesiella Mearnsii. Passing eastward toward the watershed of the Little Colorado and across northwestern New Mexico to the upper San Juan and just across the Continental Divide to the west affluents of the Rio Grande, one notices a gradual transition into an erect or ascending pod commonly a little shorter and smaller, varying in outline from ovoid (A. Rothrockii) to obovoid (Jonesiella recedens), or globose. A pod of the smaller type is more often broadly turbinate than truncate at base, and ordinarily of slightly thinner texture. In the Colorado Basin north of the San Juan River, the prevailing form of the pod is narrowly ellipsoid, narrowly oblong, or clavately ellipsoid. In this region it is nearly always erect or ascending and puberulent, either when young or permanently, but it varies from straight to gently incurved and from subterete to distinctly obcompressed and shallowly sulcate dorsally. Along the lower Gunnison River the pod shades gradually from oblanceolate to clavate and ultimately obovate in profile, thus passing insensibly into the state described above as corresponding with Jonesiella recedens. In the Rio Grande Valley from Santa Fe southward and east to the head of the Canadian and the Staked Plains, the pod of A. praelongus again assumes a narrow outline and appears wholly similar to that of the Utah plants, except that it is more often glabrous and sometimes more deeply grooved dorsally. The typus of Jonesiella Ellisiae represents this form. It cannot be overemphasized that the transition from a narrow pod to a broad one is extremely gradual and fully documented by an uninterrupted series of minor variants. Nevertheless the extreme forms are strikingly unlike; and since relatively plump or slender pods are found exclusively over extensive areas, it becomes reasonable to maintain two intergradient varieties, var. praelongus and var. Ellisiae. About nine-tenths of the material I have examined can be referred to one of these categories on a basis of a pod more or less than one centimeter in diameter. In one out of ten colonies the pods vary around a mean diameter of approximately one centimeter, and these cannot be identified except perhaps on a statistical basis.