Astragalus racemosus var. longisetus

Gullied clay bluffs, eroded shale barrens, and alluvial clay flats, especially common along creeks and rivers, locally abundant in the foothills of the southern Rocky Mountains and adjoining piedmont and higher prairies, 4500-6500 feet, in Colorado (Boulder County southward) and northern New Mexico (Colfax County); also at lower elevations, ± 3500—3800 feet, in the badlands and foothills of the Black Hills, South Dakota, and adjoining northwestern Nebraska, extending along the Cheyenne River just into eastern Wyoming, in this region passing into var. racemosus.—Map No. 46.—May to July.

Astragalus racemosus var. longisetus (with long bristles, in reference to the hyaline bracts or bracteoles) Jones in Proc. Calif. Acad. Sci. II, 5: 663. 1895.—" ... the types of this variety are in the National Herbarium. Wolf, No. 216, Apex, Colorado, June; Fort Collins, Colorado, on prairies; Sheldon, Pueblo, Colorado; Bodin and Eastwood, Denver, Colorado; Idaho, Hayden’s Survey; Moose Jaw Creek... Macoun."—Lectotypus, collected at Pueblo, Colorado, June 8, 1890, J. E. Bodin, US! Paratypus, Wolf 216, US! The Sheldon and Hayden spms. at US represent A. bisulcatus and A. racemosus var. racemosus respectively; the Eastwood and Macoun spms. are at CAS and represent var. longisetus and var. racemosus respectively.

Tium platycarpum (with flat pod) Rydb. in N. Amer. Fl. 24: 387. 1929.—"Type collected along Oak Creek, Colorado, in 1873, Brandegee."—Holotypus, NY!—Astragalus platycarpus (Rydb.) Barneby var. typicus Barneby in Leafl. West. Bot. 4: 59, Pl. 1, figs. 6, 27. 1944.

In the foothills of the Front Range in Colorado and southward interruptedly, where selenium-bearing formations are exposed, to the Arkansas Valley, the Mesa de Maya, and the sources of the Canadian in New Mexico, the var. longisetus is easily distinguished from the typical form of the alkali milk-vetch by its dorsally saccate, long-toothed calyx, consistently large flowers, and relatively ample leaflets. The bulk of Jones’s material was of this type, so that even though long bracts (or bracteoles) are not diagnostic of the variety as redefined here, the choice of lectotypus seems justified. The populations of var. longisetus found in the Black Hills and badlands of South Dakota, like those of adjoining Wyoming and Nebraska, are for the most part less distinctive; and plants technically referable to var. racemosus, as well as var. longisetus, have been collected in the Cheyenne Valley in Niobrara County, Wyoming (C. L. Porter 3973, 6919a). Several collections from eastern Nebraska, and one notable one from Chaves County, New Mexico (Waterfall 8749, OKLA) have been identified and mapped as representing var. racemosus, but show various combinations of relatively long teeth (to 4-5 mm.) with narrow leaflets and truncate calyx, or short teeth with broad leaflets. The intermediate forms are perhaps too numerous, and reduction of the variety by Rydberg (1929, p. 387) and by C. L. Porter (1951, p. 11) was possibly justified.

At the time that I published the combination A. platycarpus, I had yet to learn of the variation in the flowers of A. racemosus; and I had not identified the type-locality of Tium platycarpum, which I believed might lie in southwestern Colorado, far outside the known range of A. racemosus. Oak Creek is a small tributary of the Arkansas River in Fremont County, where var. longisetus is especially common. The typus of T. platycarpum is fragmentary, lacking the diagnostic lower stipules of sect. Bisulcati, but there can be no reasonable doubt as to its identity.