The time evolutlon of the metalliclty wlthln the Galaxy has been analysed on the base of published data for star clusters. The resulting age-metalliclty relation seems to split into two independent paths, passing the same age range over 10^10 years. The lower relationship resembles that for the Magellanic Clouds. Such a picture of the chemical evolutlon of the galactic matter is consistent wlth the observed division of the considered sample of open clusters into two groups differing in metallicity and spatial distribution, similarly to the division found for globular clusters. The metal-poor open clusters resemble metal-rich globulars. This can suggest that our galaxy has evolved from spherical metal-poor configuration represented in the considered sample of star clusters by metal-poor globulars, through a thick dlsk phase wlth the middle metallicity up to thin metal-rich disk wlth its representative
metal-rich open clusters. The transition between each of the above phases was more or less abrupt in its characteristic chemical and spatial properties.