Astragalus diversifolius 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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Type
"With the preceding.," i.e., H. junceus and H. campestris, "Sandy plains of the Colorado of the West, near the sources of the Platte." and perhaps also "in sandy places in the Rocky Mountain range towards the Oregon... Nuttall."— Holotypus, labeled by Nut
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Synonyms
Homalobus orthocarpus Nutt., Astragalus campestris var. diversifolius (A.Gray) J.F.Macbr., Astragalus junceus var. orthocarpus (Nutt.) M.E.Jones, Astragalus junceus var. diversifolius (A.Gray) M.E.Jones, Astragalus convallarius var. diversifolius (A.Gray) Tidestr., Astragalus ibapensis M.E.Jones, Atelophragma ibapense (M.E.Jones) Rydb., Astragalus reclinatus Cronquist
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Description
Species Description - Slender, weakly diffuse, with a thick, forking taproot and shortly subterranean, perhaps rarely superficial, ultimately knotty root-crown, strigulose nearly throughout with fine, filiform or somewhat flattened, straight, appressed hairs up to 0.30.6 mm. long, the herbage green or greenish-cinereous, the leaflets either pubescent on both sides or nearly glabrous above; stems several or numerous, prostrate, or decumbent with weakly ascending tips, 2-5 dm. long, for a short space buried, very slender and leafless, becoming a little stouter upward, branched or spurred at 2-6 of the lowest leaf-bearing nodes, floriferous upward, together forming loosely woven mats; stipules dimorphic, the lowest papery-scarious or early becoming so, pallid, brownish, or purple-tinged, amplexicaul and connate through half their length into a loose campanulate sheath 1-2.5 mm. long, the median and upper ones herbaceous, ovate, deltoid, or triangular-lanceolate, (1) 1.5-3 mm. long, embracing 1/3 to the whole stem’s circumference, united, if at all, at base only, commonly free; leaves (1.5) 2-5.5 (7) cm. long, 1-5 (7)-foliolate, the flattened petiole or rachis and petiole together very short, 2-20 mm. long, the linear-elliptic, linear, oblanceolate, or lanceolate, acute or acuminate leaflets all decurrent on and continuous with the rachis, the 1-2 (3) lateral pairs 0.4-4.7 cm. long, the terminal one conspicuously longer than the last pair and 1-6.7 cm. long, the grasslike blades either flat or marginally involute, carinate dorsally by the midrib, the lateral leaflets often lacking from some of the lowest and some uppermost leaves, these reduced to a simple, petioled phyllodium; peduncles slender, incurved-ascending, (2) 4-15 cm. long, mostly surpassing the leaf; racemes loosely (1) 3-8-flowered, the flowers at first ascending, spreading in age, the axis elongating, 0.5-3 cm. long in fruit; bracts submembranous, pallid or purplish, ovate or lanceolate, 0.7-2.5mm. long; pedicels at anthesis ascending, straight or nearly so, 1.8-3.1 mm. long, in fruit either ascending or geniculate at base and divaricate, little thickened, 2.5-4 mm. long; bracteoles 0; calyx 4.4—6.7 mm. long, densely strigulose with mixed black and white, largely black, or all white hairs, the subsymmetric disc 0.8-1 mm. deep, the campanulate tube 3.2-4.7 mm. long, 2.5-3.5 mm. in diameter, the subulate or triangular-subulate teeth 1-2 mm. long, the whole becoming papery, marcescent unruptured; petals greenish-white, the banner and keel-tip faintly lilac-tinged; banner recurved through 50-80°, broadly spatulate, ovate- cuneate, or suborbicular-flabellate, shallowly notched, 8-13.4 mm. long, 6.7-9 mm. wide; wings 7.7-12.1 mm. long, the claws 3.2-4.8 mm., the broadly oblanceolate or obliquely obovate, obtuse or emarginate, gently incurved blades 5.1-8.2 mm. long. 2-3.9 mm. wide; keel 7.8-11 mm. long, the claws 3.2-5 mm., the lunately elliptic blades 5.1-6.4 mm. long, 2.3-2.8 mm. wide, gently incurved through 80-95° to the triangular, subacute or obtuse, sometimes slightly porrect apex; anthers 0.5-0.75 (0.8) mm. long; pod either ascending or declined (ordinarily humistrate), sessile or substipitate, the stipe up to 1 mm. long, the body narrowly oblong or very slightly enlarged upward and oblong-oblanceolate in profile,1-1.7 cm. long, (2.7) 3—4 mm. in diameter, straight or more often slightly decurved, strongly compressed and 2-sided, the thin, green, strigulose valves becoming papery, stramineous, finely cross-reticulate, not inflexed, or inflexed (especially in the distal half) as a rudimentary septum up to 0.4 mm. wide; dehiscence apical and downward through both sutures, the valves somewhat elastically coiling; ovules 10-16, commonly 14; seeds not seen ripe.
Distribution and Ecology - Moist, often alkaline meadows, ditch banks, and swales in the sagebrush zone, 4400-6300 feet, local and apparently quite rare, upper Snake River Plains and valleys of the Lost and Lemhi Rivers in southeastern Idaho, and edge of Salt Lake Desert in northwestern Utah; perhaps also east to the upper South Platte in southern Wyoming, but not collected there in recent times.—Map No. 22.—May to July.
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Discussion
The meadow milk-vetch, A. diversifolius, is difficult to distinguish from A. convallarius by any one consistently effective differential character, and modern botanical opinion has been divided about its status. Ordinarily the leaflets are broader and of thinner texture, but they are sometimes all linear; and the pod, although broader and shorter than that of typical A. convallarius, closely resembles that of var. finitimus in size and outline. Collectively, nevertheless, the distinctive morphological features of A. diversifolius, seen in relation to a physiological adaptation to a mesophytic habitat, are ampy diagnostic. The superficial appearance of the average population is so striking that the species has been redescribed twice since Nuttall by botanists long familiar with its common xerophytic counterpart.
In Idaho the pod of A. diversifolius is precisely like that of Nuttall’s original Homalobus, and is strictly unilocular. Around the margins of Salt Lake Desert in Juab and Tooele Counties, Utah, the species is represented by a form with pod narrowly septiferous from the dorsal suture, but apparently in no other way different. It was described by Jones as A. ibapensis and referred by him to sect. Atrati (1923, p. 182), but Rydberg’s reduction of it (1929, p. 268) to the synonymy of A. diversifolius must be accepted.
In the early days of botanical exploration in the West the meadow milk-vetch was collected twice, by Nuttall on the "Colorado of the West," a term usually signifying the Green River Basin, southwestern Wyoming, and by Geyer on the "south fork of the Platte," which I interpret as a southerly branch of the North Platte rather than the South Platte of today’s maps. Apparently the species has not subsequently been collected east of the Continental Divide, or even on the Green River, and it is legitimate to question the correctness of the old labels. Except for two collections from Utah, mentioned above, all our modern collections of A. diversifolius are from the valleys of the Lost and Pahsimeroi Rivers in Custer and Lemhi Counties, and from the Snake River Plains in Blaine and Bingham Counties, Idaho, where the species must have lain directly in the path of both Nuttall and Geyer as they traveled westward to the Columbia. However the early travelers in the arid West, who followed streams and whenever possible camped within reach of grass and water, must have had opportunities, now lost forever, of seeing the mesophytic vegetation of the bottom lands and streamsides in pristine condition, and it would be rash to discount the old reports.
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Objects
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Distribution
Idaho United States of America North America| Utah United States of America North America|