Astragalus episcopus S.Watson
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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
"Southern Utah, Capt. F. M. Bishop."—Holotypus, GH! isotypi, NY, PH, US (some mixed with A. Coltoni and perhaps other spp.)
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Synonyms
Homalobus episcopus (S.Watson) Rydb., Astragalus kaibensis M.E.Jones, Lonchophaca kaibensis (M.E.Jones) Rydb.
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Description
Species Description - Stiffly wiry, apparently leafless, strigulose throughout with appressed, filiform or somewhat flattened hairs up to 0.45-0.75 mm. long, the stems and herbage green or yellowish-green, the growing tips often cinereous, the leaflets (when present) pubescent on both sides, sometimes more densely so above than beneath; stems few or solitary from a woody taproot or shortly forking caudex, simple and subterranean for a space of 2-9 (12) cm., on emergence stouter and purple-tinged, divaricately branched at the lower exposed nodes, the branches often disposed in unequal pairs in the lower axils and the more vigorous ones again branched or spurred up to the first peduncle, the internodes flexuous or abruptly zigzag; stipules dimorphic, those at the buried (and often at the first emersed) nodes papery, ovate or oblong, obtuse or subobtuse, several-nerved, 2-13 mm. long, strongly adnate to the suppressed petiole to form a bidentate sheath but incompletely amplexicaul and free, the usually smaller, herbaceous upper ones deltoid or triangular-acuminate, semi- or less than semiamplexicaul, with erect or recurved blades; leaves ascending, divaricate, or deflexed, 2-10 cm. long, most (or all) of them reduced to the grooved rachis, a few (usually low on the stems) bearing 1-4 (6) remote, opposite or scattered, linear-elliptic and subacute or narrowly oblong and obtuse-emarginate, shortly petiolulate or decurrent, thick-textured, involute or folded lateral leaflets 1-15 mm. long; peduncles erect or incurved-ascending, 6-20 (23) cm. long, surpassing the leaf; racemes loosely or remotely (4) 6-22 (30)-flowered, the flowers ascending, the axis early elongating, 3-20 (27) cm. long in fruit; bracts either scarious or firm but then early becoming pallid, triangular or lanceolate, 1.3-3 mm. long; pedicels at anthesis straight, ascending, 1.5-3 mm. long, in fruit thickened, arched out- and downward, or contorted, or more abruptly dejected, but scarcely longer, bracteoles 0-2; calyx 5.3-8.5 (9) mm. long, white-strigulose, the subsymmetric disc (0.9) 1.2-2.2 mm. deep, the deeply campanulate to subcylindric tube (3.8) 4.2-6.2 mm. long, 1.9-2.8 (3.4) mm. in diameter, the broadly subulate to narrowly lanceolate teeth (1) 1.2—2.8 (3) mm. long, the whole becoming papery, ruptured, marcescent; petals whitish commonly pink-tinged, rarely purplish, the color fugacious, appearing ochroleucous or brownish in most specimens; banner recurved through ±: 40—45°, rhombic-obovate or -elliptic, notched, 11-14.4 (15.5) mm. long, 5.8-9.4 mm. wide; wings nearly as long or up to 1.5 mm. shorter, 10-12.7 (14.3) mm. long, the claws 5-6.4 mm., the oblong-oblanceolate, -elliptic, or linear-oblong, obtuse or erose, almost straight blades 5.4-8 (8.9) mm. long, 1.2-2.7 (3.7) mm. wide; keel 9-12.3 mm. long, the claws 4.96.6 mm., the half-obovate blades 4.5-6 (6.6) mm. long, 2.1-2.7 (3.5) mm. wide, incurved through 80—95° to the rounded or exactly deltoid apex; anthers 0.5-0.65 (0.75) mm. long; pod deflexed, sessile or cuneately tapering at base into a stout stipelike neck up to 0.6 mm. long, oblong- to narrowly lance-elliptic in profile, commonly a trifle arched downward proximally and straight thereafter, (1.5) 3 3.2 cm. long, 4—7 (8) mm. in diameter, tapering and cuspidate at apex, ± strongly compressed and 2-sided but the lateral faces convex at maturity, bicarinate by the broad ventral and more slender dorsal sutures, the thinly fleshy, green or purple- tinged, glabrous or strigulose valves becoming stiffly papery, stramineous or brownish-purple, faintly reticulate (the nerves largely immersed), not inflexed; ovules 16—24 (26); seeds (little known) brown, pitted and wrinkled but sublustrous, ± 3-3.5 mm. long.
Distribution and Ecology - Barren sandy or sandy clay knolls, bluffs, and rocky talus beneath escarpments, on sandstone or in petrified forest, 4200-5200 feet, locally plentiful but apparently of bicentric dispersal: common in the San Rafael Swell and Wayne Wonderland, south to the foothills of the Henry Mountains in Emery, Wayne, and Garfield Counties, Utah; also on the Colorado River and its tributaries in Coconino and extreme northeastern Mohave Counties, from Marble Canyon west to Kanab Creek (Pipe Springs; Fredonia), south to Moenkopi Wash and the Little Colorado at Wupatki National Mounment.—Map No. 24.—May and June.
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Discussion
The Bishop milk-vetch is one of several superficially similar ephedroid astragali native to the Colorado Basin, but it is likely to be confused only with related Lonchocarpi, for these alone have similar pods combined with free lower stipules. The differential characters of A. lancearius have been stressed already in the key to subsect. Lancearii; A. xiphoides is distinguished by its more shortly campanulate calyx-tube and shorter, little or irregularly graduated petals, all about 8-9 mm. long and all very strongly recurved.
On the San Rafael and Fremont Rivers in Utah A. Episcopus is locally abundant and rather common, but in northern Arizona the known stations are few and far apart and the populations seem to be small in extent and numbers. There is no record of the species from between the mouth of the Paria and the Henry Mountains, a gap of over a hundred miles, but there seem to be no tangible differences between the plants in the two segments of the range. In Utah the pod is perhaps slightly thinner in texture when fully ripe and tends to be a little more strongly flattened laterally. The habit of growth and the flower remain essentially stable, granted a range of variation normal in any species at all widely dispersed. Jones referred the Utah material to A. lancearius and divided the Arizona material available up to 1923 between A. Episcopus and A. kaibensis, but I have come to the belief that the latter is nothing more than a minor variant of the Bishop milk-vetch. Jones and Rydberg knew A. kaibensis only from the type-collection, which consists of immature specimens. The pod was thought by Jones to be subterete or even a little grooved ventrally; his figure (1923. Pl. 64) shows the crosssection as almost circular. Riper specimens from House Rock Valley collected in recent years (e.g., Peebles & Parker 14,644; Ripley & Barneby 4856, cited above) show that the fruit in this region is indeed a little turgid, with low-convex lateral faces and an oval-elliptic section, but the sutures are both prominent and the pod could only be described as laterally compressed. Southward, on the Little Colorado (50 miles s. of Lee’s Ferry. Jones, POM: Wupatki National Monument, David Jones 345, ARIZ, US), the pod is once again strongly flattened and except for its slightly stiffer texture identical with that of the Utah plant.
The history of A. Episcopus is quickly told. The species was collected first in 1872, when Capt. Bishop was with the Powell Grand Canyon Expedition and working out of Kanab. Jones surmised that the type-locality was "probably on the western side of the Kaibab south of Kanab," and modern collections from the Fredonia-Pipe Springs area lend some support to this view. The material of A. Episcopus distributed under that name by Watson was a mixture, containing at least some fruits and probably some flowers of A. Coltoni. The latter is endemic to Utah and is there partly sympatric with A. Episcopus; the type-material may therefore have come from the general region of the Henry Mountains or even farther north. However this may be, the original mixture gave rise to considerable confusion in the past. Rydberg, basing his opinion on the isotypus at NY, transferred the name to A. Coltoni (cf. Rydberg, 1923, p. 185) and subsequently (1947, p. 33) I proposed that A. Episcopus should be discarded as a nomen ambiguum because it was based on several discordant elements. At the time of this proposal I lacked insight into the taxonomic problems posed by A. lancearius and its close kin, and I also failed to appreciate the fact that the holotypus of A. Episcopus (the material retained by Watson at GH) is entirely of the species under discussion here. It is now felt that the name can properly be salvaged for its present purpose. Confusion between A. Episcopus and A. lancearius is analyzed further under the next species.
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Objects
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Distribution
Utah United States of America North America| Arizona United States of America North America|