A monogenic mutant of Petunia hybrida R-n57 exhibits flowers with abnormal gynoecium: various malformations, such as the opening of the style and the nonprotection of ovules, or the masculinization with development of pollen sacs, anthers, and male gametophyte growing with or within ovules. The same type of abnormalities happens over and over along one inflorescential axis so that an ontogenic analysis can be conducted. Some assumptions are supported by the histocytological study: a few punctual modifications of the normal organogenesis program, recently established, and one new stage ending at the masculine or abnormal gynoecium, with homeotic members, are involved. Relations between the deflected development and female sterility are argued. Key words: flower, teratology, morphogenesis, mutant, Petunia.