Astragalus umbellatus

Title

Astragalus umbellatus

Authors

Rupert C. Barneby

Scientific Name

Astragalus umbellatus Bunge

Description

1.  Astragalus umbellatus

Low, sometimes diminutive but proportionately coarse and amply leafy, with a pluricipital root-crown giving rise to (seldom collected) obliquely ascending, subterranean, rhizome-like caudex-branches, the stems (distally), petioles, and lower leaf-surfaces thinly (or when young canescently) villosulous or villous with fine, loosely ascending and spreading, nearly straight (and sometimes a few shorter, curly) hairs up to 0.75-1.3 mm. long, the submembranous, reticulately veined leaflets bicolored, pallid beneath, green and glabrous above, the inflorescence fuscous- or black-hairy; stems erect or ascending, leafless at base, simple, (3) 5-15 (20) cm. long; stipules large, ovate, obovate, or broadly lanceolate, obtuse or subacute, several-nerved, 4-16 mm. long, the lowest united into an entire, loosely amplexicaul blade, the upper ones herbaceous (at least distally), fully amplexicaul but free, all glabrous or nearly so dorsally; leaves (2) 3-10 cm. long, the lower ones shortly petioled, the rest subsessile, with (5) 7-11 broadly ovate, rhombic- ovate, oblong-elliptic, or lance-oblong, obtuse or sometimes mucronulate and subacute, rarely subemarginate, flat leaflets (0.8) 1-3.5 cm. long, at base either rounded or broadly cuneate and often a trifle asymmetric; peduncles erect, A 10 cm. long, nearly always longer than the leaf; racemes shortly but loosely, but seldom truly subumbellately 5-11-flowered, the flowers nodding at full anthesis, the axis a little elongating, (0.5) 1—3.5 (8) cm. long in fruit; bracts membranous pallid, several-nerved, elliptic-oblanceolate or obovate, 5-10 mm. long; pedicels slender, densely fuscous-villous, at anthesis ascending, (1.5) 2.5-3.8 mm long in fruit arched outward, somewhat contorted, or deflexed, 3-5 mm. long; bracteoles 0; calyx 7.5-8.8 mm. long, villosulous (the teeth especially) with curly black, fuscous, or rarely white hairs, the strongly oblique disc 0.8-1.1 mm. deep, the pallid, broadly campanulate tube 6.3-7.5 mm. long, 3.7-5 mm. in diameter, the broadly triangular teeth 0.5-2 mm. long, the whole becoming papery, marcescent unruptured; petals cream-colored; banner gently recurved through ± 45°, spatulate, 14.4-17.7 mm. long, the rather narrow claw abruptly expanded into a suborbicular or obscurely rhombic, shallowly notched blade 8.7-11 mm. wide; wings (0-1.5 mm. shorter) 13.2-16 mm. long, the claws 7.2-10.2 mm., the oblong-obovate or oblong, obtuse, often erose, nearly straight blades, 6.7-8.4 mm. long, 2.6-3.5 mm. wide; keel (nearly always a little shorter than the wings) 13.2-16 mm. long, the claws 1.2-9.1 mm., the lunately half-elliptic blades 5.2-7.4 mm. long, 2.9-3.8 mm. wide, incurved through 45-85° to the blunt apex; anthers 0.5-0.65 mm. long; pod pendulous, stipitate, the stipe 4—7 mm. long, the body obliquely lance-ellipsoid, tapering at both ends, decidedly inflated, 1.8-2.5 cm. long, 5.5-7.5 mm. in diameter, laterally compressed at base and the ventral suture there strongly convex-arcuate and salient, thereafter a little dorsiventrally compressed, with low-convex ventral and flattened dorsal faces, the thin, densely black- or brownish-villosulous valves becoming papery-membranous, not inflexed; ovules 7-10; seeds olivaceous, purple-speckled, smooth but scarcely lustrous, 2.4-3 mm. long.—Collections: 37 (o); representative: Mexia 2080 (CAS, NY, WTU); A. & R. Nelson 3954 (NY, SMU); Galen Smith 2000 (NY); Porsild & Breitung 10,304 (NY) Frits Johansen 331a (NY).

Arctic and subarctic shores, tundra, heathy hillsides, and openings in spruce forest, sometimes on silty gravel bars along streams, and ascending to open alpine ridges in the interior, 20-4500 feet, widespread and apparently common along the Arctic Coast west of the Mackenzie River Delta to Behring Strait, south to Alaska Peninsula (Shumagin Islands), and extending up the Kuskokwim and the south forks of the Yukon into interior Alaska and southwestern Yukon; also west around the coast of Siberia to Novaya Zemlya and Kolguev Island, south to the mountains of Kamtchatka.—Map No. 1.—June to August.

Astragalus umbellatus (with flowers umbellately racemose) Bge., Astrag. Geront. 2: 29. 1869.—"Hab. in insula Nowaja-Semlia ad sinum Kostin-Schar (Al. Lehmann)."—No typus examined, but this the only Astragalus of its kind known from Novaya Zemlya and the interpretation traditional.

Phaca frigida y littoralis (of the seashore) Hook., Fl. Bor.-Amer. 1: 140. 1831.—"Arctic shores, westward of the Mackenzie River, Capt. Sir John Franklin and Capt. Back, to Cape Lisburne, on Behring’s Straits, Messrs. Lay and Collie in Capt. Beechey’s Collection."—Lecto- typus, labeled "Kotzebue’s Sound, Capt. Beechey," K!—Phaca frigida a demissa (of low growth) Ledeb., Fl. Ross. 1: 576. 1842, a superfluous substitute. Astragalus frigidus var. littoralis (Hook.) Wats., Bibl. Ind. 192. 1878. A. alpinus var. littoralis (Hook.) Sheld. in Minn. Bot. Stud. 1: 133. 1894. Phaca littoralis (Hook.) Rydb. in Bull. N. Y. Bot. Gard. 2: 176. 1901. Astragalus littoralis (Hook.) Cov. & Standi, ex Mertie in U. S. Dept. Inter., Geol. Surv. Bull. 836 E. 365. 1932, nom. nud.

Astragalus frigidus var. dawsonensis (of Dawson, Yukon) Rouss. in Contrib. Lab. Bot. Univ. Montreal 24: 47, figs. 12-14. 1933.—"Yukon: Moosehide Creek, Dawson, June 16, 1914 (specimen en fleurs, No. 259, type) et July 16, 1914 (specimen en fruits, No. 477, cotype), Alice Eastwood (type et cotype dans l’herbier de l’Universite de Montreal)."—Holotypi not examined; isotypi (Nos. 259 & 477), CAS, WS!—A. americanus X umbellatus Hult., Fl. Alaska & Yukon 1086. 1946.—"One specimen collected by Eastwood at Moosehide Creek (No. 477, US) seems to me to be the hybrid... It was described by Rousseau... as Astragalus frigidus var. dawsonensis."—US!

The tundra milk-vetch, A. umbellatus, is easily recognized in America by the entire, unifoliolate, lower stipules characteristic of sect. Phaca, by its stature dwarf in proportion to the few large, veiny leaflets, and by the nodding, cream-colored flowers which give rise to stipitate, densely dark-hairy fruits in the form of a spindle somewhat laterally compressed at base and thereafter fore and aft. The plants vary in height, those from the coast above the Arctic Circle being generally dwarf or even diminutive, whereas those of the interior, especially when found on river banks and gravelly stream beds, tend toward a taller and ranker growth.