Some of the basic concepts common to plant taxonomy, palaeobotany and palynology are discussed such as “taxon”, “taxonomic categories”, “genus and species concepts”, as well as “organ and form genera”. The development of the specifically palaeobotanical and palynological concepts of organ and form genera is briefly treated in the light of the shaping of palaeobotanical thought and methods since Adolphe Brongniart. The need for a single category of an artificial nature (i.e., form genus) is acknowledged; the need for a second category of such nature (i.e., organ genus) is questioned. The general guide lines for good palynological practice given by Faegri et al. (1950) are recommended for future use and are reprinted as an appendix to this paper.