Glabrous perennial (rarely annual) 2-7 dm, simple below the infl; lvs mostly 20-70(-100) below the infl, narrowly lanceolate to oblanceolate, the lower (or nearly all) opposite, the larger ones 1-2.5 cm נ2-5 mm, gradually reduced above; infl with ±elongate, rather stiffly ascending-spreading branches, the pedicels to 3(-5) mm; sep lanceolate, acute, the outer entire, 2-3.5 mm, the inner somewhat shorter, broader, and evidently gland-toothed; pet yellow, 4-8 mm; fr ±persistent, depressed- globose, 2 mm, commonly suffused with purple above; false septa virtually complete, glabrous, as also the septa. Dry upland woods and beaches, s. Me. to Fla., w. to s. Ont., Mich., Ill., Io., e. Kans., and e. Tex. June, July. Var. medium, found about Lake Erie and w. Lake Ontario, in s. Ont. and rarely adj. U.S., is tetraploid (2n=72) and has relatively thick, blunt lvs 3-5 mm wide; the fr tends to split at the summit only. Var. texanum (Planch.) Fernald, occupying the rest of the range of the species, is diploid and has thinner, more pointed, narrower lvs mostly 1.5-3.5 mm wide; the fr splits completely into 10 deciduous mericarps. (Cathartolinum m.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.