Astragalus reventus
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Title
Astragalus reventus
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Authors
Rupert C. Barneby
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Scientific Name
Astragalus reventus A.Gray
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Description
155. Astragalus reventus
Rather coarse, densely or loosely tufted, shortly but definitely caulescent, with a woody taproot and knotty, shortly forking caudex, strigulose or villosulous with all appressed or subappressed and straight, or all spreading and incumbent, fine, filiform or slightly flattened hairs up to 0.5—0.85 (1.2) mm. long, the herbage green or rarely grayish-silky, the leaflets glabrous or nearly so above; stems several or numerous, commonly stout and striate, erect or decumbent at base and thence ascending, (2.5) 8-18 cm. long, the main axis less than half the height of the fully grown plant, composed of 2-5 (6) developed intemodes, the longest of them (usually that preceding the first peduncle) up to 1.5-10 cm. long; stipules membranous, early becoming papery, pallid or brownish, 3.5-9 mm. long, the lowest ovate or lance-oblong, the upper triangular or lance-acuminate, all conspicuously adnate to the petiole-base, decurrent around about half the stem’s circumference, or the lowest fully amplexicaul but not connate, the margins commonly beset with a few processes; leaves (6) 8-18 (21) cm. long, with rather stiff (the upper short) petioles and (17) 23-41 rather scattered, lance-oblong or -ovate, oblanceolate, or narrowly elliptic, or (in some upper leaves) linear, obtuse, retuse, or acute, flat or folded leaflets 5-21 mm. long; peduncles stout, erect, 1-2 dm. long, surpassing the leaves; racemes 8-21-flowered, at first rather dense, early elongating and looser, the flowers loosely spreading or nodding, the axis (2.5) 4—10 cm. long in fruit; bracts membranous, lanceolate, 2.7-5.5 mm. long; pedicels at anthesis a little arched outward or recurved, 1.4—2 mm. long, in fruit erect or narrowly ascending, clavately thickened, 3-5.4 mm. long; bracteoles commonly 2, sometimes vestigial or 0; calyx (8.9) 10.7-14.8 mm. long, loosely strigulose or villosulous with black or mixed black and white or fuscous hairs, the oblique disc 0.9-1.4 mm. deep, the membranous, pallid, deeply campanulate, dorsally convex tube (6.2) 6.8-9.8 mm. long, (3.8) 4—5.4 mm. in diameter, the lance-subulate teeth (2.2) 3-5.2 mm. long, the ventral pair commonly broader but either longer or shorter than the rest, the whole becoming papery, irregularly circumscissile; petals white or creamy-white, immaculate; banner recurved in a gradual arc through nearly 90°, oblanceolate or rhombic-oblanceolate, shallowly notched, (15.2) 16.2-24 (25.3) mm. long, 6-10 mm. wide; wings (14.6) 16.2-21.3 mm. long, the claws (6.2) 7.6-10.1 mm., the elliptic-oblanceolate, obtuse or obliquely subemarginate, slightly incurved blades 9.7-13 mm. long, 2.2-3.7 (4.4) mm. wide; keel (12.1) 13-16.3 mm. long, the claws (6.2) 6.8—9.5 mm., the obliquely triangular or rarely obliquely elliptic blades abruptly incurved through 90° (rarely gentiy so through only 65°) to the rather sharply deltoid, sometimes minutely porrect apex; anthers 0.7-1 mm. long; pod erect, sessile, obliquely ovoid-acuminate to broadly lance- or oblong-ellipsoid, (1.5) 1.7—3 cm. long, 7-10 mm. in diameter, straight or a trifle incurved, rounded, broadly cuneate, or truncate at base, contracted distally into a triangular-acuminate, slightly compressed, rigidly cuspidate beak, otherwise a little obcompressed, carinate ventrally by the thick, blunt, cordlike suture, flattened or very widely and shallowly sulcate dorsally, the dorsal suture commonly prominent but thinner than the ventral one and often undulate, the green, fleshy, glabrous valves becoming stiffly leathery or woody, stramineous or brownish, transversely rugulose-reticulate and often also wrinkled lengthwise, either not inflexed or inflexed as an obscure partial septum up to 0.9 mm. wide; ovules 25-36; seeds olivaceous or deep mahogany-brown, smooth but dull, 2.7-3.4 mm. long.—Collections: 20 (o); representative: Hitchcock & Muhlick 8317 (CAS, NY, WS, WTU); Pierce & Dillon 802 (CAS, WS, WTU); Cusick 3458 (WS); Cronquist 6572 (CAS, ID, NY, SMU, TEX, WS); Peck 26,351 (RSA, WILLU).
Dry, rocky slopes, knolls, and hilltops, in open yellow pine forest, 3000-5000 feet, occasionally a little lower, locally common in the Blue Mountains of northeastern Oregon, particularly on the upper forks of the Umatilla and Grande Ronde Rivers, extending northeast into extreme southeastern Washington.—Map No. 63.—April to July, the fruit persisting into fall.
Astragalus reventus (returned, in allusion to the lapse of 48 years between the original and second discoveries) Gray in Proc. Amer. Acad. 51: 46. 1879.—"Interior of Oregon, Douglas, in fruit.... now collected in Grand Round Valley and Blue Mountains in the eastern part of Oregon, in April, 1878,... by William C. Cusick; and... in Klickitat Valley, Washington Territory, by Joseph Howell."—Cotypi, Douglas (fr.) and Cusick 593 (fl.), both GH! isotypi (Douglas, variously labeled), BM, G, K, P! the Howell collection is A. reventiformis.— Phaca reventa (Gray) Piper in Contrib. U.S. Nat. Herb. 11 (Fl. Wash.): 372. 1906. Cnemidophacos reventus (Gray) Rydb. in Bull. Torr. Club 40: 52. 1913.
The Blue Mountains milk-vetch is a rather handsome, coarse species, remarkable for the numerous, scattered, early deciduous leaflets, stout peduncles proportionately very long for the total height of the plant, and large, fleshy, persistent pods of rigidly leathery or woody texture when ripe, unilocular or nearly so. The populations vary considerably in flower-size and in orientation of the hairs on the leaves, which may be truly appressed or incumbent and villosulous. The largest flowers seem to occur toward the southwest limit of the species on the divide between the Umatilla and the Grande Ronde, and are commonly associated with a loose type of vesture. The plants flower very early in the season, and consequently there is too little material at this stage of development to draw conclusions as to the racial situation in the species.
In growth-habit and form of the pod A. reventus rather closely resembles A. reventiformis and A. conjunctus, species of sect. Conjuncti distinguished by their scarious, connate lower stipules. The first is found far to the west in the foothills of the Cascade Range, but A. conjunctus is widely dispersed in the mountains of eastern Oregon and is known to occur within a mile or two of A. reventus in southern Umatilla County. It is especially easy to distinguish when in flower, as the calyx-tube (only 2.5—4 mm. in diameter) is narrower relative to its length and thus cylindric or nearly so, and all the petals, or at least the keel-tip, are suffused with pinkish- or bluish-purple. The relationship of A. reventus to A. Sheldoni is considered below.