Synopsis of the United States Species of Lythrum (Lythraceae)

Considerable difficulty was encountered in distinguishing the species of Lythrum found in north central Texas, and in deciding on the correct names for them. To dispose of a relatively small problem (only two species were involved), it has been necessary to undertake a study of the genus in the entire United States and Mexico. Because of lack of adequate collections, and lack of field acquaintance with any of them, those of the latter region have been omitted. Only two proved of any concern in treating those of the United States; they are noted briefly under L. californicum and L. alatum. Introgression between species where the ranges meet, the occurrence of endemic minor variants (especially in L. californicum), and the considerable superficial similarity of the common and widespread species, have been responsible not only for frequent misidentifications, but in considerable part for misapplication of names. No new species are proposed, and only three species are involved in changes of application of earlier names (two of them unfortunately the commonest and most wide-ranging in the country). It is hoped that the artificial key given below will facilitate identification, but as in most difficult groups, it is important that complete specimens be used