Astragalus inversus M.E.Jones
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Authors
Rupert C. Barneby
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Authority
Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(1): 1-596.
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Family
Fabaceae
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Scientific Name
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Type
"Susanville, California, July 1, 1892, Brandegee."—Holotypus, collected by T. S. Brandegee, July 1, 1893, UC! isotypi, CAS, POM (fragm.)!
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Synonyms
Homalobus inversus (M.E.Jones) Rydb., Astragalus filipes var. inversus (M.E.Jones) Jeps.
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Description
Species Description - Slender, diffuse, sparsely leafy and somewhat junceous, with a woody taproot and shallowly subterranean, shortly forking caudex or knotty root-crown, thinly strigulose with fine, straight, appressed or narrowly ascending hairs up to 0.3-0.5 mm. long, the stems and herbage green or greenish, the leaflets usually pubescent on both sides, sometimes more thinly so or rarely glabrous above; stems several or numerous, widely spreading or prostrate, 2-5 dm. long, naked and simple at base, divaricately branched from 1-4 axils preceding the first peduncle, zigzag distally, together forming loosely woven mats; stipules 1.5-5 mm. long, dimorphic, those at the subterranean and first emersed nodes amplexicaul and connate into a papery- membranous, subtruncate or bidentate sheath, the median and upper ones herbaceous, either semiamplexicaul and free or fully amplexicaul and united by a low collar around the stem, with spreading or abruptly deflexed, triangular or triangular-acuminate free blades; leaves (3) 5-12 cm. long, all shortly petioled, with slender rachis and 5-11 remote, linear, linear-oblanceolate, -elliptic, or filiform, acute or subacute, mostly involute and retrorsely arched leaflets (2) 5-25 mm. long, those of the upper leaves commonly reduced in size, number, or both, occasionally wanting, the terminal one continuous with or obscurely jointed to the rachis; peduncles divaricate and incurved, (2) 4-20 cm. long; racemes very loosely (3) 5-15 (22)-flowered, the flowers ascending in early anthesis, then spreading and at last declined, the axis becoming (1.5) 2-10 cm. long, the fruits commonly secund; bracts submembranous, ovate-acuminate or lanceolate, 1-2.5 mm. long; pedicels slender, at anthesis ascending, straight, 0.6-1.5 mm. long, in fruit spreading, arched outward, or contorted around the axis and thence dejected, 0.8-3 mm. long; bracteoles 0-2, minute scales when present; calyx 3.5-5 mm. long, strigulose with white or black and white hairs, the subsymmetric disc 0.7-1.1 mm. deep, the reddish tube 3-4 mm. long, 2.3-2.8 (3.1) mm. in diameter, the broadly subulate or triangular, mostly obtuse teeth 0.6-1 mm. long, the ventral pair commonly shortest, the orifice ± oblique, the whole marcescent unruptured; petals pinkish- red with darker red veins, the banner tipped with white and the keel and wings with buff-yellow; banner gently recurved through 35-45°, ovate-cuneate or oval- elliptic, shallowly emarginate, 9.4—12.2 mm. long, 4.5—6.4 mm. wide, the blade fleshy-thickened in the fold; wings only slightly shorter, 8.5-11.6 mm. long, the claws 3.2-3.7 mm., the broadly oblanceolate or narrowly oblong, truncate-erose or emarginate, slightly incurved blades 5.9—7.7 mm. long, 1.7—3 mm. wide; keel 8.2-10 mm. long, the claws 3.3-3.9 mm., the obliquely triangular-lanceolate blades 5.1—6.5 mm. long, 2.1—2.8 mm. wide just above the base, thence tapering upward and gently incurved through 40—85° to the subulate, beaklike but ultimately obtuse apex; anthers 0.55-0.75 mm. long; pod pendulous (appearing horizontal from divaricate or humistrate peduncles), stipitate, the straight, slender stipe (4) 6-14 (16) mm. long, the body linear-oblong or -lanceolate in profile, (1.5) 1.8-3.5 cm. long, 3-4.5 mm. in diameter, straight or a little arched downward, shortly acuminate at both ends, strongly compressed, 2-sided, bicarinate by the filiform but salient sutures, the faces low-convex at maturity, the thinly fleshy, mottled valves becoming papery, brownish or stramineous, strigulose with incumbent hairs or glabrous beyond the puberulent stipe, not inflexed; ovules 13-17; seeds (seldom seen) about 2.5 mm. long.
Distribution and Ecology - Plains and thinly wooded hills, in dry stony basaltic or pumice soils, among sagebrush or in xeric pine forest, 4000-6000 feet, apparently uncommon (but easily overlooked), known only from northeastern California, from eastern Siskiyou and northeastern Shasta to western Modoc and southern Lassen Counties. —Map No. 31.—June to August.
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Discussion
The Lava Beds milk-vetch, A. inversus, has many technical characters in common with A. filipes, but it is easily distinguished by the few, scattered or remote leaflets, the curiously shaped keel-petals, and the mottled pod. Its sparsely leafy, somewhat rushlike growth-habit is likely to recall A. convallarius of sect. Genistoidei, a related group differing in the sessile but similarly compressed pod. The reddish-pink coloring of the petals, which fades off to white toward the tip of the banner and is variegated by yellowish wing-tips, has no match among American Astragali.
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Objects
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Distribution
California United States of America North America|