log (N/C) vs. logg for the sample stars. The evolutionary tracks are labelled by initial mass. Full lines show models with initial rotation v_init = 0.4v_crit, dot-dashed and dashed lines show models with v_init = 0.1v_crit and 0.2v_crit, respectively. Left: stars less massive than the average mass of the sample, i.e. 30 M_⊙. Stars rotating faster than 200 km s⁻¹ are highlighted by thick black circles. Right: stars with initial masses above the average for the whole sample. See text for more details