Astragalus filipes

Homalobus stenophyllus sensu Rydb. in Mem. N.Y. Bot. Gard. 1 (Fl. Mont.): 249. 1900 & in N. Amer. Fl. 24: 273. 1929; ? an A. stenophyllus T. & G., 1838, nom. ambig. Phaca stenophylla sensu Piper in Contrib. U.S. Nat. Herb. 11 (Fl. Wash.): 371. 1906.

Homalobus MacGregorii (Ernest Alexander McGregor, 1880- , entomologist, assistant curator at DS 1906-9) Rydb. in Bull. Torr. Club 50: 270. 1923.—"Near Frazier Borax Mine, Mount Pinos, Ventura County, California, June 12-14, 1908, Abrams & McGregor 219." —Holotypus, NY! isotypi, DS, G, US!—Astragalus MacGregorii (Rydb.) Tidest. in Proc. Biol. Soc. Wash. 50: 20. 1937.

Astragalus filipes var. residuus (left behind, relict) Jeps., Man. Calif. 571. 1925—"... from the Santa Rosa Mts. (Cahuilla Valley, Jepson 1469, type) to Mt. Piños."—Holotypus, collected in May, 1901, JEPS!—A. stenophyllus var. residuus (Jeps.) Barneby in El Aliso 2: 203. 1950.

In northern Nevada, southern Idaho, and over much of transmontane Oregon the basalt milk-vetch, A. filipes, is one of the few truly common astragali, often occurring in colonies of great extent, sometimes in such quantity as to color the sagebrush hillsides with a wash of creamy, spicily fragrant blossoms. Except in northeastern California, where its range overlaps those of the two immediately related Inversi keyed out above, A. filipes is the only species in its area of dispersal other than A. tenellus (with much smaller flowers and fruits) in which connate stipules are combined with stipitate, laterally compressed, unilocular fruits. Care should be taken in southern California to discriminate between it and A. trichopodus var. phoxus which has a deceptively similar pod but all stipules free.

Despite an immense latitudinal range of close on twenty degrees (31-51° N.), A. filipes is comparatively little variable in features of importance, and the fluctuation in size and shape of the leaflets or in amount and distribution of the pubescence fails to coincide with significant patterns of dispersal. A partial exception to this statement is provided by a pod glabrous or pubescent above the consistently puberulent stipe. A long, if not unbroken tradition has maintained two coordinate entities, shifting from the varietal to the specific level, based chiefly on this character. The typus of A. filipes represents, sensu stricto, a particular race of the basalt milk-vetch native to sagebrush scablands at low elevations in eastern Washington. The average plant from this region is relatively slender, with few, commonly diffuse stems, small, scattered, very narrow leaflets cinereous on both sides, and very loosely or remotely racemose, whitish or greenish-white flowers small for the species as a whole and giving rise to fruits pubescent the whole length. (C. L. Hitchcock 17,492 ID, NY, RSA, WS; H. T. Rogers 592, CAS, NY, WIS, WS; J. W. Thompson 11,665, CAS, NY, WTU). On the other hand, the picture I have formed of the Great Basin populations of A. filipes is typified by a well-furnished clump of many erect and stiffly ascending stems, leaflets mostly linear (rarely broader, exceptionally filiform), more compact fruiting racemes (3-13 rather than 5-23 cm. long), ochroleucous flowers of variable size, and a pod glabrous above the stipe (Nelson & Macbride 1029, ID, NY, RM, SMU, WS; Maguire & Holmgren 26,360, NY, RSA, TEX, UTC, 25,490, 25,870, NY, RSA, UTC, WS; Train 2942, NA, NY, TEX). While these contrasts hold good in many cases, none of them bear really close scrutiny. For example, plants of the slender northern type isolated in Nicola Valley in British Columbia may bear either glabrous or pubescent fruits (J. W. & E. M. Thompson 59, CAS, glabrous, NY, pubescent); and the same type of variation occurs on Mt. Piños in southern California (M. & G. Ownbey 2986, CAS, NY, RSA, SMU, WS, glabrous; C. B. Wolf 11,129, CAS, NY, pubescent). Furthermore, in the Columbia drainage of northeastern Oregon, especially on the Deschutes and lower John Day Rivers, the prevailing form of A. filipes is of the erect southern type but bears pods about as often pubescent as glabrous; and there are a few scattered records of a puberulent pod from the lake country of southeastern Oregon, even from northern Nevada (Heller 10,631, CAS, NY). There is sound reason to believe that racial differentiation is actively at work in A. filipes, but it is of no practical use to break up the species into subspecific units without a better means of discriminating between them.

Several attempts have been made to maintain a separate taxonomic niche for the populations of A. filipes found in four restricted and mutually distant areas in the mountains of southern California and northern Baja California, probably because these are so dramatically disjunct from the main range of the species. The var. residuus was supposed originally to differ from A. filipes in its oblique pod, with straight ventral and low-convex dorsal sutures. A pod of this sort is found on a few other collections from the San Jacinto Mountains (Munz 15,125, CAS), but it is not characteristic of all southern Californian material and occurs sporadically also in the Great Basin. I look back with perplexity at my statement (1950, l. c.) that A. stenophyllus var. residuus could be distinguished from the typical sort by more densely pubescent foliage and strigulose pod, for neither point is true of the majority of specimens that I have examined since. The typus of Homalobus MacGregorii has glabrous fruits combined with leaflets pubescent both above and beneath, but this combination of pubescence-characters is only one of several present in southern California, and all can be matched in fine detail with material from the Great Basin. As a last instance of variation in vesture, I must cite a collection from northern Baja California (Harbison 44,793, RSA) which includes examples of leaflets either glabrous or pubescent above. The populations of A. filipes at the northern and southern limits of its range are especially plastic as regards the vesture of the pod, and indeed of the whole plant, even though they are isolated in environments hostile to their expansion under contemporary climatic conditions. They have the appearance of relicts contradictorily rich in biotypes.

The Basin type of A. filipes with pod ordinarily glabrous has passed in recent monographs and in most of the floristic literature of the past fifty years under the name A. stenophyllus T. & G., and rejection of the latter in favor of the later A. filipes requires explanatory comment. The name A. stenophyllus T. & G., 1838, originated as a legitimate substitute for the later homonym A. leptophyllus Nutt., 1834, and is based on material collected by Nathaniel Wyeth somewhere in western Montana or eastern Idaho during the early summer of 1833. The Wyeth specimens at PH near Nuttall’s label "Astragalus * leptophyllus. Heads of the Missouri." to which is added in an old hand, not Nuttall’s, "Nutt. from Wyeth." The duplicate in the Torrey herbarium (NY) bears the further annotation "June 16," a potentially significant date to which I shall return in a moment. These two sheets and the duplicate at BM consist of several stems, all severed well above the base and bearing racemes of flowers at full and early anthesis. In my opinion they might with equal probability represent either one of two species, A. filipes or A. (Reventi-arrecti) atropubescens. The latter is quickly distinguished in normal circumstances by its free lower stipules and erect, trigonously compressed, fully bilocular pod, but every diagnostic feature is lacking from the typus of A. leptophyllus. According to Gray the ovary of Wyeth’s plant is unilocular, but I find a like ovary in genuine A. atropubescens at the same immature stage, the septum apparently developing pari passu with the exterior walls of the fruit. Even if the specimens are indecipherable of themselves, it might seem possible to establish their identity by comparison of what is known of Wyeth’s route with the ranges of the two species in question, but here again we run into difficulties. The pertinent segment of Wyeth’s journey (as described by McKelvey, 1955, p. 513) extends from the middle of May, when he was traveling southward up the Bitterroot River in what is now Ravalli County, Montana, to mid-June, when he reached the floor of the Snake River Plains by way of the valley of the Little Lost River in eastern Idaho. Within this period Wyeth had crossed the Anaconda Range near Gibbons Pass and descended into the Big Hole Basin, the one and only point, it may be noticed, where he actually touched upon the "Heads of the Missouri." Turning west from the Big Hole, he had crossed the Bitter- roots and, having reached the Salmon River near the mouth of the Lemhi, had continued south up the Salmon and the Pahsimeroi to the head of the Little Lost. At this point, on the Pahsimeroi-Little Lost divide, Wyeth passed out of the known range of A. atropubescens into that of A. filipes, and he clearly had opportunities of collecting either species. If Nuttall’s label at PH is to be interpreted literally, the typus of A. leptophyllus was probably collected on the Big Hole in Beaverhead County, Montana, and can only represent A. atropubescens. If the date on the ticket at NY is correct and Wyeth reached the Snake River Plains by the middle of June, the typus was probably collected in the valley of Little Lost River on the way down to the Snake, and can then be identified with some assurance as A. filipes. In ordinary years it would be difficult to find plants of A. filipes in such young flower as late as June 16, but no record is available of local conditions in the spring of 1833. The best that can be said of A. leptophyllus, unless a more complete specimen exists, is that its typus might be interpreted with about equal justice in the sense of either species, and the name can properly be discarded as a potential source of error and continuing controversy. The specific epithet was first associated with the glabrous-fruiting phase of A. filipes by Rydberg in his Flora of Montana (1900, I.e.), at a time when A. atropubescens was very poorly known. If Rydberg guessed aright—and he was influenced, I suspect, by herbarium annotations of E. P. Sheldon—the plant was surely not from Montana. If the plant was from Montana, the guess was wrong. There is no obligation to respect a tradition based on such nebulous data. Cf. also Appendix I, No. 6.