Astragalus cymboides 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(2): 597-1188.
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Family
Fabaceae
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Scientific Name
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Type
"No. 5658q. July 21, 1894, Cottrell’s Ranch, Henry Mts. ... No. 5464j. June 16, 1894, Huntingdon, Utah, in clay, 5000° alt. No. 5445f. June 16, 1894, near Emery, Utah, 7000° ..."—Lectotypus (Barneby, 1947, p. 449), Jones 5464j, POM! isotypus, NY!
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Synonyms
Xylophacos cymboides (M.E.Jones) Rydb., Astragalus amphioxys var. cymbellus M.E.Jones
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Description
Species Description - Low, tufted, acaulescent or nearly so, perennial but sometimes flowering the first season, densely strigose-strigulose with straight or largely straight, appressed and (nearly always, especially on the petioles and peduncles) some looser, ascending hairs up to 0.8-1.3 mm. long, the herbage cinereous or silvery-canescent, the leaflets equally pubescent on both sides, the vesture sometimes turning greenish-golden on the upper side when dry; stems 1—several, mostly reduced to sessile crowns, if elongating then prostrate, up to 2 (3) cm. long, the internodes mostly concealed by stipules, none over 5 mm. long, mostly shorter; stipules submembranous, becoming firmly papery, ovate, deltoid- or broadly lance-acuminate, 3—8 mm long, semiamplexicaul; leaves 2.5—8 (10) cm. long, with deciduous or weakly persistent petiole and (5) 7—13 (15), or (in some early leaves, or in all leaves of seedling plants) only 1—5, obovate, elliptic, or broadly oblanceolate, obtuse or subacute, flat leaflets 3—13 (20) mm. long; peduncles rather stout, 2—8 cm. long, ascending at anthesis, arcuate-procumbent or prostrate in fruit; racemes shortly but loosely (3) 4—9 (12)-flowered, the flowers ascending, the axis little elongating, 0.5-2 (2.5) cm. long in fruit; bracts thinly herbaceous becoming papery, ovate- to broadly lance-acuminate, (1) 1.5-4 mm. long; pedicels ascending, straight or a little arched in age, at anthesis 0.7-2.3 mm., in fruit thickened, 2.5 mm. long; bracteoles 0; calyx 7.6-10.2 (14.6) mm. long, strigulose with black or mixed black and white hairs, the slightly oblique disc 1.1-1.6 (2.8) mm. deep, the cylindric or rarely cylindro-campanulate tube 5.9-8 (11) mm. long, 2.7-3.7 (4.5) mm. in diameter, the subulate teeth 1-2.3 (3.4) mm. long; petals commonly whitish or yellowish, with white- or lilac-tipped wings, sometimes all suffused with dull lilac, rarely all pink-purple, the keel-tip always maculate; banner recurved through ± 40°, broadly rhombic-oblanceolate or spatulate, shallowly notched, 15.4-18.4 (24) mm. long, 8-10 (14.5) mm. wide; wings 14.7-17 (22.8) mm. long, the claws 7.6-9 (12.8) mm., the narrowly lanceolate or linear- oblong, obtuse, nearly straight blades 8.2-10 (11.5) mm. long, 2-3 mm. wide; keel 12.6-15.1 (20.2) mm. long, the claws 7.8-9.2 mm., the half-obovate blades 5.5-6.7 (8.8) mm. long, 2.5-3.1 mm. wide, abruptly incurved through 90-95° to the rounded apex; anthers 0.6-0.8 mm. long; pod ascending (humistrate), narrowly oblong to oblong-elliptic in profile, straight or a trifle oblique (either suture the more convex), 1.7-3 (3.5) cm. long, 6-9.5 mm. in diameter, cuneate or rounded at base, contracted distally into a short, erect or slightly declined, triangular-cuspidate beak, fleshy and subterete when first formed, becoming strongly compressed laterally in ripening, ultimately bicarinate by the prominent, thick sutures, low-convex toward the middle of the two faces, the thick, green, densely strigulose valves becoming stiffly papery or somewhat cellular-spongy, the stramineous, faintly reticulate, longitudinally wrinkled exocarp at length exfoliating along the length of the ventral suture from the cellular mesocarp and ultimately recurving in the form of 2 horizontally spreading vanes; dehiscence of the firmly papery endocarp apical and finally downward through the ventral suture; ovules 39-57; seeds brown or orange-brown, pitted, sublustrous, 2-2.4 mm. long.
Distribution and Ecology - Cobblestone bluffs, river terraces, and on saddles or along draws in gullied clay hills, in loose gravelly clay alluvia, 4900-5800 feet, reportedly (Jones, ex char., but probably in error) up to 7000 feet, locally plentiful but known only from the north and northwest edge of the Colorado Basin on the San Rafael, Price, and Green Rivers in Emery, Carbon, and Grand Counties, Utah.—Map No. 93. —Late April to June.
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Discussion
The canoe milk-vetch, A. cymboides, is closely related to A. amphioxys, differing principally in the pod, which when ripe is almost straight, laterally compressed, and of a light pithy texture. Its mode of dehiscence by exfoliation of the exocarp is characteristic and unique in the genus. The ranges of A. cymboides and A. amphioxys overlap in Emery County, and flowering specimens are sometimes difficult to assign to their species. The flower of the canoe milk-vetch is ordinarily smaller and of paler color, but we have a few ambiguous examples, already mentioned in the preliminary revision (Barneby, 1947, p. 449). Measurements of the relatively large, bright purple, amphioxys-like flowers of these puzzling specimens have been included (in parentheses) in the foregoing description, but it remains an open question as to whether they really represent part of the normal range of variation. The type-collection of var. cymbellus consists of a mixture of flowering A. amphioxys and typical A. cymboides in fruit, and the same mixture may have occurred unrecognized more than once. It has been suggested that A. cymboides may hybridize with A. amphioxys var. vespertinus, but the hypothesis needs testing in the field.
The range of the canoe milk-vetch is apparently defined at its northern limit by the cliffs of the Tavaputs Escarpment, an obstacle which has been a barrier to the spread of many species in the Colorado Basin. It was reported, on the basis of a single specimen in flower, from Dinosaur Monument (Graham, 1937, p. 247), but this record is probably mistaken.
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Objects
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Distribution
Utah United States of America North America|