Monographs Details: Astragalus panamintensis E.Sheld.
Authors:Rupert C. Barneby
Authority: Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(2): 597-1188.
Family:Fabaceae
Discussion:

306.  Astragalus panamintensis

Low, slender, tufted or loosely matted, caulescent or in the first season sub- acaulescent perennial, with a taproot and intricately forking caudex with pliant branches up to 1-15 cm. long beset with a loose thatch of wiry-filiform, persistent petioles, silvery-canescent nearly throughout with fine, appressed hairs up to 0.25-0.45 mm. long, the leaflets about equally pubescent on both sides; stems of the year 1-5 cm. long, composed of several developed internodes up to 1 (2) cm. long but mostly shorter; stipules herbaceous becoming papery, with prominent midrib, deltoid or lance-acuminate, 1-3 (4) mm. long, the lowest decurrent around half or more of the stem, free, the upper less so, all more thinly hairy dorsally (sometimes with black hairs) than the canescent stem; leaves (1.5) 2-12 cm. long, slender-petioled, with 5-9 (11) distant, linear-elliptic, acute and mucronulate, flat or folded, dorsally keeled, caducous leaflets 2—12 (14) mm. long; peduncles ascending, subfiliform, (0.5) 1-6 cm. long, mostly much shorter than the leaf; racemes very loosely 1—4-flowered, the flowers ascending, the axis (0) 1.5—3.5 cm. long in fruit; bracts ovate or lanceolate, 0.8—2 mm. long; pedicels at anthesis 0.8-2 mm. long, in fruit ascending, more or less contorted, not thickened, 1—2.5 mm. long, finally disjointing; bracteoles 0; calyx 4.6—8.5 mm. long, densely white- and sometimes partly black-strigulose, the subsymmetric disc 0.7-1.3 mm. deep, the rather narrowly campanulate tube (2.7) 3-4.3 mm. long, (1.7) 1.9-2.8 mm. in diameter, the lance- or linear-subulate teeth 1.5-4.4 mm. long; petals pink-purple with pale claws; banner recurved through ± 45, 8.2—14 mm. long, the cuneate claw expanded into an ovate-elliptic, notched blade 4.8—7 mm. wide; wings 7.1—11.1 mm. long, the claws 2.8—4.6 mm., the narrowly oblong or oblanceolate, obtuse, nearly straight blades 4.8—7.5 mm. long, 1.4—2.6 mm. wide; keel 6.6—8.7 mm. long, the claws 3—5 mm., the half-obovate blades 3.4-5 mm. long, 2-2.3 mm. wide, abruptly incurved through 90-95° to the bluntly deltoid apex; anthers 0.4—0.5 mm. long; pod spreading or ascending (commonly humistrate), sessile, oblong-elliptic or -oblanceolate in profile, a trifle decurved or almost straight, 8—18 mm. long, (2.3) 3.4—4.7 mm. in diameter, contracted distally into a shortly deltoid, laterally compressed beak, otherwise obtusely trigonous, keeled ventrally by the prominent suture, openly sulcate dor sally, the lateral angles rounded, the thin, pale green but purple-speckled, densely strigulose valves becoming papery, stramineous, faintly reticulate, inflexed through the pod’s lower ½ or ? as an incomplete septum 0.7-1.3 mm. wide; seeds orange-brown, smooth or sparsely pitted, scarcely lustrous, 1.8—2.4 mm. long.— Collections: 8 (i); representative: Jones (from Panamint Canyon) in 1897 (CAS, NY, POM); J. T. Howell 4006 (CAS); Alexander & Kellogg 2662 (NY), 2806 (UC); Munz 20,573 (NY); Ripley & Barneby 2958 (RSA).

Forming mats on ledges and in fissures of dry limestone cliffs, sometimes seeding down but apparently not persisting on stony canyon bottoms, 4000-7100 feet, with piñon and juniper, rare and local, known only from the Panamint, Last Chance, and Inyo Mountains, Inyo County, California.—Map No. 96.— April to June.

Astragalus panamintensis (of the Panamint Mountains) Sheld. ap. Cov. in Contrib. U. S. Nat. Herb. 4 (Death Valley Rep.): 87. 1893.—"... No. 606, Death Valley Expedition; collected April 13, 1891, in Surprise Canyon, Panamint Mountains, Inyo County, California, by Frederick V. Coville."—Holotypus, Coville & Funston 606, US (2 sheets)! isotypi, DS, GH, K, MINN, NY, UC!—A. atratus var. panamintensis (Sheld.) Jeps., Man. Calif. 575. 1925. Tium panamintense (Sheld.) Rydb. in N. Amer. Fl. 24 : 396. 1929.

The Panamint milk-vetch is an altogether remarkable little plant, notable for its repeatedly forking caudex, many slender, incurved branches which are beset with wiry, flexible, marcescent petioles, ultimately forming an involved mass not unlike an untidy bird’s-nest. From the tips of the caudex-branches arise the young shoots which bear a few leaves composed of some two to four distant pairs of narrow, pointed leaflets; these dry up and disjoint from the rachis at about the same time as the fruit reaches full maturity. The pod is small, somewhat obliquely and narrowly oblong-ellipsoid, bluntly triquetrous with ventral suture prominent and dorsal face shallowly excavated. Both pedicels and pods disjoint in age, but the pod often becomes caught in the tangled caudex and there dehisces apically at first, then downward through the ventral suture, and finally at base. In the station known to me, below Aguerreberry Point in the Panamint Mountains, A. panamintensis is confined to crevices and ledges of almost vertical limestone cliffs, where it is associated with the endemic Tetracoccus ilicifolius Cov. & Gilm. From all the reports I have, the habitat is characteristic of the species.