Bactris is a Neotropical genus of high floristic importance, which needs morphological data to support the construction of a correct infrageneric classification. In this research, the inflorescences and flowers of Bactris acanthocarpoides Barb and B. hirta Rodr. Mart., are morphoanatomically characterised and the floral ontogeny in each of these taxa is presented in order to provide useful biological information that contributes to such classification. The results are analyzed in the context of reproduction and evolution of the palms. To achieve this, we use light and scanning electron microscopy. The distribution of appendages on the prophyll, the development of staminodes in the pistillate flowers of B. acanthocarpoides, the presence of tector trichomes on the sepals of this species, the greater scleromorphism and the presence of papillose exothecium in B. hirta, as well as the location of the vascular bundles in the perianth parts, are characters that allow distinguishing the taxa. The ontogenetic study reveals the acropetal development of the inflorescences, as well as the formation of one subtending bract for each flower of the triad and one for each triad; likewise the sequence of centrifugal development of the stamens and the formation of the gynoecium synascidiate at the base and simplicate at the top. Additionally, the histological arrangement of each floral organ was characterized and all the appendages observed were described.