Top:log  (N/C) (by number) as a function of log  (N/O). The expected trends for the case of CN and CNO equilibrium are shown by the dashed lines. Bottom: log  (N/C) (by number) as a function of log g. The two components of HD 166734 are represented by red dots, whilst the sample of Galactic supergiant stars analyzed by Bouret et al. (2012) and Martins et al. (2015) is represented by black dots. The evolutionary tracks are from Ekström et al. (2012) and are computed for a rotational rate (initial over critical) of 0.4. We use evolutionary tracks with initial masses larger than 10 M_⊙.