Astragalus subcinereus

  • Title

    Astragalus subcinereus

  • Author(s)

    Rupert C. Barneby

  • Scientific Name

    Astragalus subcinereus A.Gray

  • Description

    42. Astragalus subcinereus

    Diffuse or prostrate, slender or quite coarse and leafy, villosulous or hirsutulous with incurved-ascending, sinuously incurved, or horizontal to slightly re- trorse, straight hairs up to 0.25-0.6 mm. long, the stems and herbage greenish, cinereous, or rarely canescent, the leaflets bicolored, brighter green above, either equally pubescent on both sides or medially glabrescent to subglabrous above; stems prostrate, decumbent, or weakly assurgent, (0.8) 1.5-7 dm. long, slender, naked, and subterranean for a space of (1) 2-10 (15) cm., above ground becoming stouter and commonly branched at the first or at each of 1-6 nodes preceding the first peduncle, floriferous upward from below or near the middle, flexuous or zigzag distally; stipules dimorphic, the lower ones papery, pallid, connate into a campanulate, loosely or closely amplexicaul, shortly bidentate sheath 1.5-4.5 mm. long, the rest firmer, herbaceous or sometimes foliaceous, broadly lanceolate or deltoid from a wide, amplexicaul base, obscurely or not connate, 2 6.5 mm. long, the blades commonly reflexed; leaves ascending, divaricate, or reflexed, 1.5-8.5 cm. long, shortly petioled or the uppermost subsessile, with (9) 13-21 (23) narrowly oblong-oblanceolate, oblong, oblong-obovate, or broadly obovate-obcordate, obtuse, emarginate, or retuse, flat or folded leaflets 2-16 mm. long; peduncles incurved-ascending or straight and divaricate, 1.5-8 (10) cm. long; racemes (5) 10-37-flowered, at early anthesis rather dense, the flowers spreading or declined, the axis ± elongating, (0.7) 1-7 cm. long in fruit; bracts papery-membranous, triangular, lanceolate, or linear-setaceous, 1-3 mm. long; pedicels at anthesis ascending, 0.5-1.1 mm. long, in fruit either strongly arched outward, divaricate, or variously contorted, a little thickened, 1-2.5 mm. long; bracteoles 0, rarely a minute scale; calyx (3.4) 3.8-6.3 mm. long, hirsutulous, villosulous, or loosely strigulose with white or mixed black and white hairs, the slightly oblique disc (0.5) 0.7-1.2 mm. deep, the campanulate tube (2.3) 2.5 3.6 mm. long, 1.9-3.2 mm. in diameter, the triangular-subulate or subulate-setaceous teeth (0.9) 1.1-2.9 mm. long; petals whitish or dull yellowish, commonly veined or suffused with pale lilac or brownish-purple, the keel sometimes faintly maculate; banner gently recurved through 45° (or further in withering), obovate- cuneate, rhombic-obovate, or subflabellate, (6.2) 6.6-9 mm. long, (4.2) 4.5-6.2 mm. wide; wings (0.7 mm. longer to 0.9 mm. shorter) 6.1-8.7 mm. long, the claws 2.6-3.6 mm., the linear-oblong, oblong, or narrowly oblanceolate, obtuse, truncate, or erose-emarginate, nearly straight blades (4) 4.2-5.9 mm. long, (1.4) 1.6-2.2 mm. wide; keel (5.7) 6-7.7 mm. long, the claws (2.5) 2.7-3.6 (3.8) mm., the half-obovate blades (3.5) 3.7-4.5 (4.9) mm. long, 1.8-2.4 mm. wide, abruptly incurved through (80) 85-95° to the sharply deltoid or broadly triangular, slightly porrect apex; anthers (0.4) 0.45-0.6 mm. long; pod widely spreading or declined, subsessile, broadly ovoid-ellipsoid, narrowly or plumply and obliquely ellipsoid, or subglobose, strongly inflated, (1) 1.2-2.7 cm. long, (6) 7.5-13 mm. in diameter, rounded or truncate at base and then contracted or cuneately tapering into an obscure, stipelike neck 0.3-1 mm. long, contracted distally into a short, triangular, erect or rarely declined, laterally flattened beak, otherwise subterete to quite strongly obcompressed, openly sulcate ventrally and sometimes also (but shallowly) dorsally, the thinly fleshy, green or purple-tinged, brightly red-mottled valves becoming firmly papery or papery-membranous, brownish, cross-reticulate, densely to quite thinly villosulous or loosely strigulose with spreading or incurved hairs; ovules (10) 12—20; seeds brown, sometimes purple-speckled, smooth, dull, 1.9-3.1 mm. long.—Collections: 16 (ii); representative material cited below.

    Open flats in yellow pine forest, brushy or wooded hillsides among oaks and in juniper-piñon forest, mostly 6000—8800 (9000) feet, descending (in Nevada) to sandy valley floors at 5500 feet, locally plentiful in scattered stations: Kaibab and Kanab Plateaus, northern Coconino and Mohave Counties, Arizona; Virgin- Sevier watershed in western Kane County, Utah; Needle Mountains and upper Muddy River Valley in eastern Lincoln County, Nevada.—Map No. 15. May to September.

    Astragalus subcinereus (grayish) Gray in Proc. Amer. Acad. 13: 366. 1878. Mokiak Pass in the northwestern part of Arizona, near the Utah boundary, Dr. E. Palmer, 1877. — Holotypus, Palmer 117 of the 1877 collection, GH! isotypi (some labeled "s.w. Utah"), K, MO, NY, PH, US!—Phaca subcinerea (Gray) Rydb. in Bull. Torr. Club 40: 47. 1913.

    Astragalus Sileranus (Andrew Lafayette Siler, 1824-1898, Mormon rancher, collected extensively in s. Utah) Jones in Zoe 2: 242. 1891.—"Collected by me on June 23, 1890 in Sink Valley, southern Utah, at about 7000 feet altitude."—Holotypus, POM! isotypi, CAS, GH, MO, NY, US!—Phaca Silerana (Jones) Rydb. in Bull. Torr. Club 40: 47. 1913.

    Astragalus Sileranus var. cariacus (from Cariacus, a genus of deer, in allusion to the type- locality) Jones in Proc. Calif. Acad. Sci. II. 5: 642. 1895.-"No. 6036. September 12, 1894, Elk Ranch, Utah, 7000° alt.," the data expanded later (Jones, 1923, p. 197) to "Elk head Ranch on the upper Virgin River," apparently in w. Kane County.—Holotypus, POM (3 sheets)!

    The Siler milk-vetch, A. subcinereus, varies considerably in stature, in amplitude of the herbage, and in orientation of the hairs throughout the plant-body. The species is known from Arizona through well-documented specimens only from the Kaibab and Kanab Plateaus, where it ranges from the piñon-belt at 6000 feet upward into open parklands in yellow pine forest at about 9000 feet. The typus is said to have originated at Mokiak Pass, but Palmer’s labels are so often imprecise that it may have been collected at some distance from the pass itself. The species has not been seen there in recent years, in spite of particular search (cf. A. artipes, supposedly collected with it). At the lower elevations in Arizona, the plants are loosely strigulose with sinuously incurved hairs and the stems are relatively short and weakly ascending. Plants from the pine belt are prostrate, with stems often longer, up to 6.5 dm., but sometimes no more than 1.5 dm. long; and at the same time the vesture varies from sinuously incurved to spreading or retrorse and straight. The peduncles may be either incurved or straight and divaricate, but in Arizona the leaflets are consistently narrow, about 2—13 mm. long and 1-3 mm. broad. The pod in this area is usually small, 1-2, rarely 2.3 cm. long, and papery or papery-membranous in texture (Eastwood & Howell 1064, CAS, NY; Jones 6052, POM, NY; Kearney & Peebles 13,682, CAS).

    On the Sevier-Virgin divide in Utah the prevailing phase of A. subcinereus (= A. Sileranus sens. strict., including var. cariacus) is a coarser, more leafy plant than the Arizona type, with weakly diffuse or prostrate stems 3-7 dm. long, sometimes hanging down in festoons from steep clay banks in the oak brush. Its range extends down to 5700 feet and up into pine forest at about 7000 feet, where the plants become truly prostrate and loosely matted. Here the leaflets are normally of a broad type and deeply notched, about 6-16 mm. long and up to 4-10 mm. broad, and the vesture is consistently composed of horizontal or retrorsely directed hairs. The upper stipules are broader in Utah than in Arizona, commonly foliaceous and broader than the stem, and the peduncles are characteristically divaricate. The rather firmer- walled pod varies from 1.5 to 2.8 cm. in length, a comparatively narrow, fusiform fruit over 2 cm. long and 5-8 mm. in diameter being the only diagnostic feature of the inconsiderable var. cariacus. The populations in Utah can be distinguished collectively from those of Arizona only by the broader leaflets, and it seems best to follow Jones in considering the plants in these two areas as conspecific in the narrowest sense, although tending to diverge in several minor characters (Jones 25,429, CAS, POM; Ripley & Barneby 4798, CAS, RSA; Holmgren & Tillett 9659, RSA).

    In southeastern Nevada A. subcinereus is represented by a third, slightly different type of plant found in low, sandy valleys among sagebrush at about 5500 feet. Here the stems and foliage are densely and canescently villosulous with sinuous or curly subappressed hairs mixed with longer, incurved-ascending ones. The relatively stiff assurgent stems are 2-3.5 dm. long. The leaflets vary from broad to narrow (2-5 mm. wide). The firmly papery pod is 1.3-2.5 cm. long. This appears to be a xerophytic ecotype but has no character peculiar to it other than the comparatively dense pubescence (Train 2632, NY; Ripley & Barneby 6337, CAS, GH, NY, RSA).

    It should be emphasized that the range of variation in the flower-parts, ovule- and leaflet- number, and in other organs, is nearly identical throughout the range of A. subcinereus, which must be regarded as a somewhat polymorphic species composed of many minor variants.

    As already mentioned under the preceding species, the epithet subcinereus has been universally applied in recent literature to A. fucatus. There is no question, however, that Palmer 117, typus of A. subcinereus, represents the Arizona phase of A. Sileranus. The present disposition of the name is consistent with all that is known of the dispersal and ecology of the two species concerned; A. fucatus is native to the high sandstone deserts to the east and south of the Colorado River, far distant from the type-locality of A. subcinereus which, whether Palmer s label is interpreted as literally or only approximately correct, must lie well within the known area of A. Sileranus. Misunderstanding of the typus of A. subcinereus arose partly from the circumstance that the remaining flowers are abnormal, as may be seen by comparing their calyces with those persistent at the base of successfully ripening fruits. The former are greatly enlarged and, like the petals, distorted and fleshy-thickened. Flowers of this sort, which have been observed in many species of Astragalus, are host to the mycelium of a rust and ultimately the ovary ripens into a more or less amorphous capsular structure filled with powdery black spores. Gray’s description of the flowers as "greenish with a purple tip" was probably taken from diseased flowers, and Rydberg’s key character of "deltoid calyx-teeth," employed in North American Flora to distinguish A. subcinereus, can be traced at least in the first instance to the same source.