A revision of Celtis subg. Mertensia (Ulmaceae)

A revision of the neotropical subgenus Mertensia of the ulmaceous genus Cel tis is presented. This group is a clear-cut entity characterized by the pre sence of thorns and/or domatia, as well as by bifid stigmas. The species ar e difficult to separate and numerous species, subspecies and varieties have been recognized. In the present treatment the number of species is reduced to six, including a new and thornless species, C. loxensis, Descriptions o f the subgenus and species, a key to species, a list of synonyms, and distr ibution data are presented.