As has been stated in the introduction of the second part, this third part will include the remainder of the American part of the tribe Eupodostemeae of the subfamily Eupodostemoideae which was not treated in part I, viz. the genera Oserya, Devillea, Ceratolacis, Mniopsis, Podostemum and Castelnavia. Included are the dubious genera, and it also contains additions and corrections to part I, latin descriptions of new taxa, a list of collectors’ numbers in this part, new references to the literature, and a general index to the third part. The attention of the reader is drawn to a publication of SZAFER (1952) in which a fossil Podostemacea from Europe has been described. As I have not seen the material it is at present impossible to judge the value of the discovery though it seems highly improbable that Podostemaceae ever lived in Europe.