Evolutionary tracks of our models in the log g_pol versus log T_eff plane. For estimating the gravity of the theoretical track, we used the gravity at the pole. The gravities for the observed stars are those deduced from spectroscopy. Different kinds of points are used for stars with various surface nitrogen over carbon ratios. The stars labelled with numbers correspond to the objects, discussed in the text. The typical error bars are depicted in the lower right hand corner.