The infected cells of Vicia sativa root nodules were observed by transmission electron microscopy, which showed that there were some vesicles appearing near the plasma membrane and the infection threads of the infected cells and they continuously moved toward the central vacuoles and came close to one another to form vesicle groups. When the groups arrived at the central vacuoles, the tonoplast near them invaginated to form protrusions. The protrusions finally separated from the vacuole membrane and formed ...