Surface abundances as a function of projected rotational velocity (dubbed Hunter diagram; Hunter et al. 2008b) for the boron depletion factor (left) and for the nitrogen enhancement factor (right). The background contour is the predicted number distribution from a single star model population of early B-type main sequence stars, which is based on the Salpeter (1955) initial mass function for M_i = 5 − 20 M_⊙ stars, the rotational velocity distribution from Dufton et al. (2013), and a constant star formation rate. The color indicates the relative number of models in each bin, normalized to the maximum value in each panel. Evolutionary tracks for 12 M_⊙ stars with different initial rotational velocities are shown, whose surface rotational velocities are multiplied by π/4. The crosses in the lower right corners show the typical errors in the observed quantities. See Brott et al. (2011b) for the LMC metallicity counterpart for the Hunter diagram for nitrogen.