in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 13(2): 338. 1849.
Ariz., Calif., Colo., N.Mex., Okla., Tex., South America, naturalized in s Africa and e Australia.
Varieties 3 (1 in the flora).
Guilleminea densa var. densa has been reported from several U. S. states (e.g., J. T. Kartesz and C. A. Meacham 1999). J. Henrickson (1987) implicitly rejected those records, stating that the variety “as considered here is widespread in South America, naturalized in southern Africa, and Queensland, Australia, but does not occur in North America.”