Callisia (Commelinaceae), as currently recognized, is a genus of about 20 species confined to the New World tropics and subtropics.  A molecular phylogeny using the chloroplast gene ndhF, and the chloroplast trnL-F spacer region, has shown that Callisia is polyphyletic.  Additional molecular studies are in progress.  It is proposed to collect morphological, anatomical and cytological data  for separate and combined phylogenetic analyses.  The purpose of this study is to circumscribe Callisia, to produce a phylogeny of its species, and to determine the relationships of the various components of Callisia sensu lato to each other and to the other genera of subtribe Tradescantiinae (Commelinaceae, tribe Tradescantieae).