The study of the action of M.L.O., etiologic agents of Stolbur disease, was undertaken by inoculatingVinca roseathrough grafting, when the first full-bloom flower appeared. The mature anthers were successively harvested. The mycoplasmas interfere on the different tissues of the anther far from the sieve tubes of the connective where they are located. The external and middle layers: epidermis, endothecium and mesothecium become undifferenciated, and then hyperplasied, while the internal layer, tapetum and the sporogenous cells degenerate. The different stages of the degeneration of the sporogenous cells and of the adaxial “pellicule” correlated to the evolution of the flowers at the time of inoculation of the disease are described here. Altered pollens with an hypertrophied intine, pollens reduced to their modified exine skeleton and exine residues fusing together and with the locular “pellicule” were observed successively. Finally remnants of pollen grains only exist as an interparietal sporopollenin deposit while the mesothecial cells acquire secretory properties. These results are discussed in the light of bibliographical data concerning different cases of sterility from genetic and viral origins.