Inflorescence and floral structure ofPetalonyx linearis are described to assist in understanding homologies among the diverse flowers ofLoasaceae. The inflorescence consists of racemose axes, along which each individual flower is recaulescent with its subtending leaf. Both floral vascularization and appendage initiations show a set of variations. The pseudomonomerous gynoecium may be derived from a triplacental condition. Nectary position, on a collar on which the perianth and androecium are inserted, appears homologous to the ovarian dome position of the nectary among otherLoasaceae.