These poorly understood plants are locally abundant in subxeric to xeric open woods and edges on calcareous soils across east-central states (Coulter & Rise 1900; F), mostly in the Interior Low Plateaus but with possible outliers as far as s. Ont., Pa. and Va. (NY: Page & Prince William Cos.)..However, there has been disagreement about the circumscription of this taxon; mapping here is somewhat tentative since there may be intergradation with var. garmanii; Several authors (B, F, M, W; B.E. Wofford, D. Estes & M. Brock, pers. comm.) have segregated var. angustifolium (or "chapmanii") from typical barbinode, but D could make no consistent division in Ind. From a provisional review (see also F), var. angustifolium may be distinguished from var. garmanii (and typical barbinode) as follows: leaflets of basal leaves cut into linear or oblanceolate segments (versus ovate to lanceolate, coarsely toothed or cleft); leaflet segments (cut at least halfway to midrib) at first fork of stem numbering 15-75 (versus 9-15), oblanceolate (versus ovate to lanceolate), 2-10 mm wide (versus 5-50 mm); leaflets usually grayish-granulose green (versus dull or deeper glossy green) and densely hispidulous along all veins below (versus less hispidulous to glabrous along smaller veins). Fruits may be generally smaller than garanii and more hispidulous on margins. Var. angustifolium has often been confused with T. pinnatifidum; see notes under that name.