Astragalus missouriensis var. missouriensis

Variable in habit as described for the species; calyx 9-12 (14.3) mm. long, the tube 6.3-9 (9.3) mm. long, 3.3-4.6 (4.9) mm. in diameter, the teeth 1.4—3.3 (5.3) mm. long; banner (14.5) 16-22 (24) mm. long, (7.2) 8-12.5 mm. wide; wings (13) 13.6-19.8 (23.3) mm. long, the claws 6.8-10 (10.8) mm., the blades 8-11.1 (12.2) mm. long, 2.4-3.7 (4) mm. wide; keel (11.5) 12.8-17.3 (18.5) mm. long, the claws 6.8-10 mm., the blades (5.3) 6-8 (9) mm. long, 2.6-3.8 mm. wide; pod 1.5-2.7 (3) cm. long, (4) 5-9 (10) mm. in diameter, obtuse or sometimes cuneate at base, abruptly contracted distally into a subulate, pungent beak 1.5—4 mm. long, at first subterete or a trifle dorsiventrally compressed, when ripe somewhat laterally compressed and subquadrangular, bicarinate by the straight, parallel, or subequally convex, thickened, salient sutures, the middle of the valves transversely dilated and obtuse-angled; ovules (33) 40-50 (56).— Collections: 198 (xxv); representative: Macoun 4204 (GH, NY), 4205 (GH, MINN, NY); Moyer (from Granite Falls, Minnesota) in 1910 (GH, MINN, OB); Hitchcock & Muhlick 11,812 (CAS, RSA, WS); C. L. Porter 5336 (CAS, TEX); Horr E530 (OKLA, SMU, TEX, WS); W. A. Weber 3275 (CAS, TEX, WS); C. F. Baker 417 (GH, NY, POM); Fendler 149 (GH, NY); Thurber 142 (GH); Ripley & Barneby 4206 (CAS, RSA); B. & H. Jesperson 2656

Prairies, bluffs, and gullied hillsides, in dry open places, on a variety of sedimentary and alluvial soils but most abundant and vigorous on limestones, shales and sandstones, southward often on gypsum, ascending to 7300 feet in the Rocky Mountain foothills and to 7800 feet in northern New Mexico, widespread and common over the Great Plains from southern Alberta and southwestern Manitoba to northwestern and trans-Pecos Texas, east to the Missouri Valley in western Iowa, central Kansas, and western Oklahoma, west to the upper Missouri in Montana, to Yellowstone Park, and thence south along the Rocky Mountain piedmont to the Rio Grande Valley; extending west in New Mexico and southwestern Colorado to the headwaters of the San Juan River.—Map No. 94.—Late March to July, according to altitude and latitude.

Astragalus missouriensis (of the Missouri River) Nutt., Gen. N. Amer. Pl. 2: 99. 1818. —"On hills throughout Upper Louisiana..." Lectotypus, labeled ‘‘Louisiana, Bradbury, 1811-12.," BM! isotypus, labeled "Louisiana, Nuttall, from Lambert’s herb.," PH (herb. Pursh.)! probable isotypus, labeled "Nuttall ex herb. Lambert.," NY!—Tragacantha missouriensis (Nutt.) O. Kze., Rev. Gen. 946. 1891. Xylophacos missouriensis (Nutt.) Rydb. ap. Small, Fl. S. E. U. S. 620, 1332. 1903. A. missouriensis var. typicus Barneby in Amer. Midl. Nat. 37: 444. 1947.

Astragalus melanocarpus (with black pod) Nutt. Fraser’s Cat. 1. 1813, nom.; Richards., Bot. Append. Franklin’s Jour. 746 (in separate 28). 1823, nom.; Hook., Fl. Bor.-Amer. 1: 150. 1831, in syn.

Astragalus missouriensis ß T. & G., Fl. N. Amer. 1: 331. 1838—"In the Rocky Mountains, Nuttall."—Holotypus, NY!

Astragalus missouriensis fma. longipes (with long peduncles) Gand. in Bull. Soc. Bot. France 48: xv. 1902.--"S. Dakota ad Piedmont (A. Pratt).--Holotypus, collected by Alice D. Pratt in June, 1895, LY! isotypi, GH, MINN, WIS!

Astragalus missouriensis fma. microphyllus (small-leaved) Gand., l.c. 1902 ("microphylla").—"A. Nelson exs. no. 1227...Hab. Wyoming, ad Laramie (A. Nelson)."—Holotypus, dated May 20, 1895, LY! isotypi, RM, WS!

Astragalus missouriensis fma. leucophaeus (white and fuscous, the calyx-hairs of mixed color) Gand. in op. cit.: xvi. 1902 ("leucophaea").—"Hab. Colorado, ad Fort Collins (C. Crandall)."—Holotypus, dated May 24, 1898, LY! a probable isotypus from Fort Collins, Crandall in 1898, NY!

The Missouri milk-vetch, an astragalus common over the higher plains east of the Rocky Mountains, was first encountered in September, 1804, by Lewis and Clark (No. 36, PH), but was described from plants collected seven years later by Nuttall and Bradbury. Nuttall applied two epithets to the species, A. missouriensis being first listed in the Fraser Brothers’ catalogue as A. melanocarpus, in reference to the fruit which turns black after dehiscence. There are Nuttall specimens from the Platte labeled by Nuttall himself as A. melanocarpus (BM, K); but although the name was listed by Hooker and by Richardson, it was never associated with a description except as a synonym. A plant in the Torrey herbarium (NY) labeled A. melanocarpus by Nuttall formed the basis of A. missouriensis ß of Torrey & Gray.

Over the greater part of its range var. missouriensis, with the exception of A. lotiflorus, is the only low tufted or subacaulescent milk-vetch with pinnate foliage and dolabriform vesture. It may be distinguished at all seasons either by its longer, narrower flower and subcylindric calyx-tube or by the straight, at first terete but at length laterally compressed pod which often remains attached to the plant on a withered peduncle well into the second year. In New Mexico its range closely approaches and even overlaps to some extent that of the related and habitally similar A. amphioxys; in this region well-formed fruits are required for positive identification. The typical Missouri milk-vetch is subject to considerable variation in the size of the flower and pod. The smallest flowers are found chiefly northward from the Fortieth Parallel, whereas the largest are prevalent only on calcareous or gypseous soils toward the southern limit of the species-range. Intergradation between the extremes in flower-size is gradual and complete, offering no convenient point at which the material examined could be divided into two natural series. An especially handsome form of var. missouriensis, seen in flower in the foothills of Guadalupe Peak in western Texas, remains in my memory as one of the showiest North American Astragali.

A remarkable form of A. missouriensis, locally common on barren clay hills about Pagosa Springs in Archuleta County, Colorado, deserves special mention and a brief description:

Caulescent, the stems and caudex-branches together 7-20 cm. long; stipules 2-11.5 mm. long, all fully amplexicaul and connate; bracts submembranous, lance-acuminate or -caudate, 4-10 mm. long; calyx 7.8-10 mm. long; banner 19-20.5 mm. long; pod oblong-ellipsoid, straight, about 1.7-2 cm. long, glabrous or very sparsely pubescent along the ventral suture and on the beak; ovules 33—40.—Collections: Bethel, Willey & Clokey 4181 (WS); Ripley & Barneby 7585 (RSA).

In general appearance these plants are reminiscent of A. humistratus var. humistratus with which they have in common technical attributes of connate stipules and conspicuous bracts of thin texture; but the pod, except that it is glabrous or nearly so, is precisely that of A. missouriensis in form, texture, and compression. It is probably no coincidence that A. humistratus reaches its northern limit at Pagosa Springs (Bethel & al. 4172), for the material is persuasively suggestive of a hybrid origin. Unfortunately we lack fruit sufficiently mature to show whether it disjoints or not at full maturity, so an attempt to interpret the status and relationships of what is now apparently a self-perpetuating entity is best postponed until the problem can be studied in the field.