The karyotype analysis ofPeumus boldus reveals a remarkable differentiation of chromosomes in size and form. C-banding pattern and interphase nuclei are discribed and compared with other genera. The great variation in leaf-shape and growth-form is continuous and correlated with the very diverse habitats of the species. The recognition of infraspecific taxa is therefore not recommended. The lower leaf surface is very uniform within the monotypic genus and ± similar with that ofSiparuna. The different evolutionary strategies ofPeumus and related genera are discussed and show a different eco-systematic situation than inMollinedia andSiparuna.