Age versus M_V (as a proxy for mass) for Galactic OCs (triangles) and GCs (filled circles). Clusters in other galaxies have been marked with stars with differing numbers of branches: LMC (four), Small Magellanic Cloud (SMC, five), Sagittarius (six), and Fornax (seven). Clusters for which either multiple sequences in the colour−magnitude diagrams, chemical inhomogeneities, or both have been detected are in green, whereas clusters without either are in red. In magenta are clusters for which there are doubts about the existence of chemical inhomogeneities. Clusters not properly studied are in grey. Clusters studied here are encircled. Lines of constant mass for different metallicities have been superimposed (See text for detail).