The early development of the stamens in Stemona and Stichoneuron is similar, in spite of significant differences in the adult stages. Moreover, as the peculiar gynoecia in both genera are chiefly similar, their mutual affinity seems substantiated. It is concluded that Stichoneuron is very close to Croomia, so that these genera can be merged. However, Pentastemona is different. In its androecium it shows a corona-like development of the basal staminal region (like Peliosanthes, Convallariaceae). Therefore, the removal of Pentastemona from the Stemonaceae is corroborated. The late differentiation of its stamens into extensions that contact the stigma, as well as the inferior position of the ovary, suggest a relationship with Trichopus (Trichopodaceae) and Stenomeris (Stenomeridaceae).