Astragalus gibbsii Kellogg
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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
“... from the Sierra Nevada, near the head waters of Carson river... G. W. Gibbs."—Holotypus, CAS!
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Synonyms
Tragacantha gibbsii (Kellogg) Kuntze, Homalobus gibbsii (Kellogg) Rydb., Homalobus plummerae Rydb.
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Description
Species Description - Rather stout and leafy, with a shortly subterranean, knotty root-crown or caudex, villosulous nearly throughout with fine hairs up to 0.5-0.8 mm. long, those of the stems and petioles mostly straight and horizontally spreading, those of the leaves sometimes similar but as often incumbent and curly, the herbage canescent or rarely greenish-cinereous, the leaflets pubescent on both sides but often more thinly so above, the upper face paler green than the lower; stems numerous, decumbent or prostrate, 1.5-3.5 dm. long, naked and slender at base, becoming stouter and flexuous distally, simple or commonly spurred at 1-4 nodes preceding the first peduncle; stipules 1.5-5 mm. long, dimorphic, those at the lowest nodes small, scarious, fully amplexicaul and connate into a cup- or collar-like sheath, the median and upper ones herbaceous, ± semiamplexicaul-decurrent, free, with triangular or triangular-lanceolate blades; leaves (1.5) 3-9.5 cm. long, spreading or recurved, the lowest shortly petioled, the uppermost subsessile, with (7) 11-19 broadly or narrowly cuneate, obovate-cuneate, or more rarely oblanceolate, retuse, flat or loosely folded leaflets 4-20 mm. long; peduncles rather stout, incurved-ascending, 3-10 (12.5) cm. long, either shorter or longer than the leaf; racemes 10-30- flowered, dense at early anthesis, the flowers early nodding and retrorsely imbricated, becoming looser, the axis elongating, 2.5-10 cm. long in fruit; bracts submembranous, ovate or broadly lanceolate, 1.3-3 (4.5) mm. long; pedicels (densely villous) erect or ascending, straight or nearly so, at anthesis 1.5-2.2 mm., in fruit little thickened, 2.1-43 mm. long; bracteoles 2, triangular or setaceous; calyx 9.5-12.3 mm. long, villosulous or villous-tomentulose with white and sometimes a few fuscous or black hairs, the strongly oblique disc 1.3-1.7 mm. deep, the broadly and deeply campanulate, ovoid-campanulate, or subcylindric tube 7.6 9.8 mm. long, 4-5.5 mm. in diameter, convexly arched dorsally and gibbous behind the pedicle, the broadly subulate, lance-triangular, or deltoid teeth 2.3-3.7 mm. long, the ventral pair commonly longest and always broadest, the orifice oblique, the whole becoming papery, marcescent unruptured; petals dull yellow, the banner somewhat fleshy-thickened in the fold; banner sigmoidally arched, 14-17 (18) mm. long, the long-cuneate, tapering claw incurved proximally to conform with the curve of the calyx, abruptly expanded into an ovate, transversely oval, or suborbicular, openly notched, strongly recurved or reflexed blade 7-9.2 mm. wide; wings as long to 1.7 mm. longer than the banner, 14-18.3 mm. long, the claws 7.5-10.3 mm., the obliquely obovate or broadly lance-oblong, obtuse or undulate-emarginate blades 7.5-9.1 mm. long, 3-4.3 mm. wide; keel 12-15 mm. long, the claws 7-9.7 mm., the half-obovate blades 5.3-6.4 mm. long, 3.2-3.6 mm. wide, abruptly incurved through 90-95° to the bluntly deltoid apex; anthers 0.6-0.8 (0.85) mm. long; pod essentially pendulous but sometimes humistrate and then apparently ascending, stipitate, the straight, slender or upwardly thickened stipe (7) 10-22 mm. long, the lunately or falcately oblong, narrowly oblong-ellipsoid, or linear-oblong body 2.2-3 cm. long, (4) 4.5-8 mm. in diameter, incurved through ± ¼-½-circle, cuneate or cuneately tapering at base, abruptly contracted distally and cuspidate at apex, laterally compressed, bicarinate by the salient, thickened, often narrowly winged ventral and thinner but often undulate dorsal sutures, the lateral faces transversely distended and convex at maturity, the fleshy, green or purple-mottled valves becoming stramineous, stiffly leathery, reticulate, rather densely villosulous with spreading or incumbent hairs, not inflexed; ovules 18-30 (34); seeds (little known) brown, sometimes purple- speckled, sparsely pitted, dull, 2.3-2.7 mm. long.
Distribution and Ecology - Sagebrush valleys, silty meadow flats, and openings in yellow pine forest, in dry sandy or sandy clay soils mostly of volcanic origin, 4150-6000 feet, locally plentiful in scattered stations along the east base and foothills of the Sierra Nevada in southeastern Lassen, eastern Plumas, and eastern Sierra Counties, California, south, becoming rarer, through extreme southern Washoe and Ormsby Counties, Nevada, reentering California in Alpine and Mono Counties.—Map No. 28.—May to July.
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Discussion
The Gibbs milk-vetch is closely related to A. curvicarpus, and the two species have been treated by Jones (1923, p. 140) and subsequently by Jepson (1936, p. 366) as no more than varietally distinct. However even where their ranges come into close contact in northeastern California, A. Gibbsii differs from A. curvicarpus in the longer, looser vesture, longer calyx- teeth, proportionately shorter banner, and broader pod of thicker texture which is transversely dilated at maturity to a degree never approached by allied species. The connate stipules provide a qualitative criterion separating A. Gibbsii from all other Collini. In the form of the stipules, as well as in some aspects of the legume, A. Gibbsii is reminiscent of A. bicristatus (of the transverse ranges of southern California), but its nodding flowers and basally saccate calyx are characteristic of the present section. Whether the connate stipules of A. Gibbsii have been acquired by an independent mutation, or present a primitive character lost by its near kindred, or alternatively have been derived by introgression from another source, is of great theoretical interest but remains an open question. It is probably no more than a coincidence that the rare A. (Bicristati) Webberi is endemic to a small area in the Sierra Nevada immediately to the west of A. Gibbsii; but this species could have supplied the factor for connate stipules.
Flowering specimens of A. Gibbsii and A. collinus are easily confused, for they are similar in general appearance and in details of the pouched calyx and modified banner. Material of the Gibbs milk-vetch collected by Anderson and Lemmon was misidentified by Gray, in Botany of California, as A. cyrtoides, a synonym of A. collinus; and reports of A. Gibbsii from westcentral Idaho and from the Blue Mountains in Oregon have persisted in the literature until recent years. The ordinarily straight, always narrower, and more strongly flattened pod readily distinguishes A. collinus, not to mention the impressed reticulation of the pod-valves, the free stipules, and other small differences.
In Lassen County the petals of A. Gibbsii are distinctly yellow when fresh; this seems to be true of the species as a whole. As in some forms of A. curvicarpus, particularly its var. subglaber, the banner is fleshy-thickened in the fold of the blade and turns brown or brown- spotted unless dried with great dispatch. The flowers are heavily but disagreably fragrant.
The precise southern limit of the species has not been determined. There is only one record from Mono County (R. King in 1911, ND) and this lacks exact locality-data; it has been mapped arbitrarily in the northern part of the county. The Gibbs milk-vetch may occur in the upper Walker Valley and is to be sought in that neighborhood.
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Objects
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Distribution
California United States of America North America| Nevada United States of America North America|