Upper panel: logg – T_eff diagram for the SMC O stars (squares) and the SMC B stars (orange circles) of Hunter et al. (2009). The evolutionary tracks are from Georgy et al. (2013). The dashed horizontal lines mark the log g limits used in the lower panels. Lower panels: log (N/C) as a function of projected rotational velocity (v sin i). Left panel: stars with logg > 3.95, right panel: those with 3.1 < log g < 3.95. We have omitted stars from the Hunter et al. sample that have only upper limits on the nitrogen abundance.