Bahia oppositifolia (Nutt.) Gray
[= Picradeniopsis oppositifolia]
Annotated by Lincoln Ellison.

Montana: Custer County: Hogback Well, U.S.R.L. Experimental Station; Near Well.
46.3333357° N, 105.8761135° W
Coordinate Source: USGS-website.
In colonies on disturbed soil along road. This plant seems to be a newcomer - conspicuous this year for the first time, although old growth shows it here in 1936. Used Fort Keogh Livestock and Range Research Station for lat/long. Herbarium of the Forest Service, U.S. Department of Agriculture. MRC 3645 Phenology: Flowers.

Lincoln Ellison 3405, Jun 24, 1937
MONTU, Accession: 137960