Joannesia is a genus of plants in the family Euphorbiaceae, first described as a genus in 1798. The entire genus is endemic to Brazil. Species 1. \n* Joannesia heveoides Ducke - Amazonas State in Brazil 2. \n* Joannesia princeps Vell. - eastern Brazil (Distrito Federal, Espírito Santo, Minas Gerais, Rio de Janeiro)species in homonymic genus In 1807, Persoon used the same name, Joannesia, to a very different plant. He thus created an illegitimate homonym, contrary to the rules of nomenclature. So the one species name that he had created in this illegitimate genus had to be renamed, as follows: