ABSTRACTPneumatophores of Mauritia vinifera Mart. were collected from six month-old plants maintained submerged in fresh water to induce pneumatophore formation. Twenty day-old pneumatophores had a quite prominent root cap. The epidermis was composed of hexagonal cells, tangentially distributed along the cylindric surface of the organ. In transverse section these pneumatophores had a simple epidermis over several layers of sclerified parenchyma, which covered an aerenchyma with large intercellular spaces. The endodermal cells had Casparian strips. The vascular cylinder was polyarch, with a pith and surrounded by a unisseriate pericycle. Anatomically the 4 monthold pneumatophores were similar to the younger ones, except for the absence of the epidermis. The epidermis is replaced by a protective tissue, whose lignified and suberized cells projected themselves outwards, giving it a filamentous aspect. There was no accumulation of starch or tannins in the pneumatophores, except for the presence of statoliths in the root cap. No lenticels were observed in pneumatophores of M. vinifera. The main function of the pneumatophores of M. vinifera is to allow gas exchange, facilitating the supply of oxygen to the submerged root portions.