Astragalus bicristatus A.Gray
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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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Synonyms
Homalobus bicristatus (A.Gray) Rydb., Astragalus bicristatus var. tetrapteroides M.E.Jones
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Description
Species Description - Low but vigorous, rarely quite slender, strigulose nearly throughout with fine, straight, appressed or subappressed hairs up to (0.35) 0.4-0.6 (0.7) mm. long, the herbage green or cinereous, the leaflets varying from equally pubescent on both sides to densely cinereous or quite glabrous above, the inflorescence ± black-hairy; stems several or numerous, decumbent and assurgent, 2-4 (4.5) dm. long, commonly branching near the purplish, leafless, shortly subterranean base, the stronger branches bearing spurs or branchlets at 1—3 nodes preceding the first peduncle, more rarely simple; stipules 1.5—4 mm. long, dimorphic, the lowest early becoming papery-scarious, the very lowest 1—3 pairs amplexicaul and connate into a bidentate sheath or low collar, the rest ovate or deltoid-acuminate, cauline, the herbaceous blades deflexed; leaves 3-11 (13.5) cm. long, the lower shortly petioled, the upper subsessile, with (11) 13—21 (23) opposite or scattered, linear, linear- elliptic, or narrowly oblong, more rarely oblong-elliptic or oblanceolate, mostly obtuse or retuse, sometimes subacute, folded, involute, or rarely flat leaflets (2) 4-25 (27) mm. long, the terminal one usually jointed like the rest, sometimes (in some upper leaves) continuous with the rachis; peduncles rather stout, 5-12 (15) cm. long, usually longer than the leaf, incurved-ascending; racemes loosely or (at very early anthesis) closely 5-15 (20)-flowered, the flowers ascending, the axis becoming 1.5-6 (9) cm. long in fruit; bracts membranous, triangular-ovate, 1.5-2.5 mm. long; pedicels at anthesis straight, ascending, 0.8-1.7 mm. long, in fruit thickened, arched outward, (1) 1.4-2.5 mm. long; bracteoles 2, minute, rarely 0; calyx 8.1-10.1 mm. long, loosely strigulose with black or mixed black and white hairs, the oblique disc 1.3-2 mm. deep, the submembranous, pallid, deeply campanulate tube 5.8-7.6 mm. long, 3.8-4.7 mm. in diameter, the subulate teeth 1.8-3.3 mm. long, the ventral pair often shortest and broadest, the orifice oblique; petals greenish-white, drying ochroleucous, immaculate; banner recurved through 45-50° (further in withering), rhombic-elliptic or -lanceolate, cuneate at base, broadest below the middle, the blade tapering upward, notched at the narrow apex; wings 13-16 mm. long, the claws 6.5-7.8 mm., the narrowly lance- or rarely oblance-oblong, obtuse or erose-emarginate blades 7.2-9.7 mm. long, (2) 2.3-3 mm. wide; keel 12-13 mm. long, the claws 6.5-7.6 mm., the half-obovate blades 5.4-7 mm. long, 2.9-3.7 mm. wide, abruptly incurved through 90-95° to the sharply deltoid apex; anthers 0.6-0.85 (0.95) mm. long; pod pendulous, stipitate, the stout, downwardly arched stipe (6) 8-12 mm. long, the body obliquely oblong- or clavate-ellipsoid, 2-4 (4.3) cm. long, 5-8.5 (9) mm. in diameter, either cuneate at base or (more often) acuminately tapering from above the middle into the stipe, cuneately contracted distally into a triangular-acuminate, rarely long-acuminate, stiffly cuspidate, laterally compressed beak, the whole either gently lunate-incurved its whole length, or straight below and then abruptly hamate, or evenly arched through ½ -circle, or exceptionally coiled into a ring, the body fleshy and subterete or a trifle obcompressed when first formed, becoming more strongly dorsiventrally compressed in ripening (and the more so the more incurved), at length bicarinate by the salient sutures, the lateral angles transversely dilated and obtuse-angled, the thick, smooth, green, glabrous valves becoming brownish, stiffly leathery or subligneous, coarsely rugulose-reticulate and wrinkled lengthwise distally, not inflexed; dehiscence primarily through the stipe and upward 1/3 way through both sutures, also tardily apical, through the beak; ovules 26-33; seeds brown, purple- speckled, smooth, dull or sublustrous, 2.8-3.8 mm. long.
Distribution and Ecology - Rocky ridges, stony sagebrush flats, lake shores, canyon benches, and openings in pine forest, 5850—8000 (reportedly 9000) feet, local but forming colonies in the transverse ranges of southern California, in particular about the east end of the San Gabriel Range (West and Prairie Forks of San Gabriel River to Swartout Valley) and northeast end of the San Bernardino Mountains (Bear and Holcomb Valleys and the north slope of Sugarloaf Mountain), Los Angeles and western San Bernardino Counties.—Map No. 70.—May to August.
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Discussion
The most distinctive feature and chief ornament of the two-keeled milk-vetch, A. bicristatus, is its massive, pendulous, long-stipitate pod. The stipe turns down out of the calyx in a gentle arc and the body, which is commonly broadest a little above the middle and tapers downward into the stipe, is variably incurved, forming in profile a crescentic, abruptly hooked, or more rarely an annular figure. The body of the pod is subterete when first formed, although the cavity is already somewhat transversely dilated, and the characteristic bluntly quadrangular cross-section is achieved only as the fleshy tissues collapse in drying and reveal the salient sutural keels. The foliage of A. bicristatus varies in amplitude, the leaflets fluctuating between truly linear and oblong-elliptic; but the leaflets are disposed so distantly along the rachis that even the broadest type presents a sparsely leafy aspect. A minor variant with leaflets canescently strigulose on the upper face and greenish beneath occurs with the commoner thinly hairy type. The var. tetrapteroides was based on typical material of the species examined in the living state.
The two small areas of dispersal to which A. bicristatus is apparently restricted hardly exceed ten miles in diameter and lie about thirty-five miles apart. In both the species is associated with A. Douglasii and with a locally endemic variety of A. lentiginosus. These have much smaller flowers than A. bicristatus and sessile, bladdery pods of papery texture.
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Objects
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Distribution
California United States of America North America|