Astragalus cimae 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
"Collected by Mrs. Brandegee at Cima on the edge of Nevada near the Charleston Mts. 1915." —Holotypus, dated "June, 1915" and attributed to T. S. Brandegee, POM! isotypi, UC-JEPS (K. Brandegee), UC (T. S. & K. Brandegee)! The spm. at GH, dated "May 5, 191
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Description
Species Description - Low, rather coarse, with a knotty root-crown or shortly forking, superficial caudex, the stems and thick-textured, glaucescent foliage glabrous or nearly so, the margins of the stipules sometimes beset with straight, subappressed hairs up to 0.2-0.5 mm. long, the inflorescence thinly black-strigulose; stems usually few, commonly 1-3 (7), decumbent with ascending tips, simple, (3.5) 6-24 cm. long, the lowest internodes short or subobsolete, the upper 2-6 developed and up to (1.5) 2.5-9 cm. long; stipules 5-10 mm. long, membranous, pallid, or the uppermost thinly herbaceous, all several-nerved, the lower ones broadly ovate, mostly obtuse, amplexicaul-decurrent around ± 3/4 the stem’s circumference, the upper ones narrower, the uppermost lance-ovate or ovate-acuminate, mostly acute; leaves 4.5-11 cm. long, all but the lowest subsessile, with 11-21 (23) obovate-cuneate, ovate, broadly oblong-elliptic, or suborbicular, obtuse or emarginate, flat leaflets 5-20 mm. long; peduncles 3-8.5 cm. long, incurved-ascending at anthesis, reclinate in fruit; racemes loosely 10-25-flowered, the flowers at first ascending, sometimes loosely declined in age, the axis elongating, (3) 4-12 cm. long in fruit; bracts membranous, pallid, broadly ovate-acuminate or lanceolate, (3) 4-6 mm. long; pedicels at anthesis ascending, 0.6-1 mm. long, in fruit a little thickened, arched outward, 1-2 mm. long; bracteoles 2, minute or up to 2 mm. long; calyx 5.9-7.6 mm. long, strigulose with black or mixed black and white hairs, the oblique disc 0.9-1.5 mm. deep, the membranous, purplish, deeply campanulate tube 4.5-5.6 mm. long, 2.8-3.6 mm. in diameter, the erect or spreading, subulate or triangular-subulate teeth 1.3-2.5 mm. long; petals reddish-purple with white or lilac wing-tips and a pale, striate lozenge in the banner, drying violet; banner 12-15 mm. long, the long-cuneate claw abruptly expanded into a rhombic-ovate, shallowly or deeply notched blade 6.6-8.7 mm. wide; wings 10.6-13 mm. long, the claws 5.1-6 mm., the narrowly oblong, obtuse or obliquely emarginate, nearly straight blades 6.1-8.4 mm. long, 2.5-3.2 mm. wide; keel 9.5-10.6 mm. long, the claws 4.8-5.8 mm., the broadly half-obovate blades 5.2-6 mm. long, 2.5-3.2 mm. wide, rather abruptly incurved through 80-90° to the rounded apex; anthers 0.55—0.75 mm. long; pod loosely spreading-ascending (commonly humistrate), stipitate, the stout, clavate stipe equaling or surpassing the marcescent calyx, the body oblong to broadly oblong-ovate in profile, nearly straight to greatly incurved, truncate at base, contracted distally into a deltoid or triangular-acuminate, cuspidate, laterally compressed, unilocular beak, otherwise obcompressed, openly sulcate ventrally and sometimes also dorsally, variable in size, texture, and degree of inflation, 1.5—3.7 cm. long, 8—21 mm. in diameter, the glabrous, glaucescent valves at first green suffused or dotted with red, stramineous when ripe, inflexed as a complete or nearly complete septum, but this often narrow proximally and widened upward; dehiscence apical, tardy, after falling; ovules (27) 30—36; ripe seeds unknown.
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Discussion
The Cima milk-vetch consists of two varieties, each restricted to a known range of less than ten miles diameter, and these areas of dispersal lie about one hundred and fifty miles asunder in the eastern and northern Mohave Desert. The plants of the two races are almost identical in every macroscopic detail up to the pods, but these differ greatly in size, texture, and degree of inflation. The fruit of var. cimae is of moderate dimensions, at first fleshy and almost solid (the small cavity filled with ovules and pulpy filaments) and becomes subligneous at maturity, when the sutures stand revealed as thickened, salient ribs. By contrast the pod o var. sufflatus, which is thin-walled and greatly inflated, with a large, empty cavity surrounding the ripening seeds, is a third larger or more; its ripe valves are chartaceous and its sutures remain slender and little prominent. Differences of this magnitude have traditionally sufficed, and in some cases still serve, as specific or even subgeneric criteria; some botanists may prefer to regard var. sufflatus as a species apart. However that may be, the two entities provide an example of a mutation or series of mutations involving primarily and to all appearances exclusively a modification of the gynoecium’s post-ovarian development. The Cima milk-vetch illustrates the fact that, in Astragalus, an important evolutionary step affecting the pod can occur independently of gross modifications in the plant-body, a point which has far-reaching implications for those interested in tracing natural relationships (as opposed to formalistic rearrangements) in the genus and in establishing a sound system of classification in accord with phylogenetic truth.