Abstract: | Chains of multiple heterocysts form in Anabaena und Calothrix filaments on treatment with rifampicin. The multiple heterocysts form irrespective of whether the rifampicin treatment is given in combined nitrogen-free or supplemented medium. This suggests the possibility of involvement of a species of RNA or of protein as intracellular heterocyst inhibitor and indicates that some latent pattern-determining mechanism may operate in the combined nitrogen medium. |