Surface boron abundances plotted versus polar gravity for 12 M_⊙ models with initial υ_ini/υ_crit between 0 and 0.4. The orange continuous curve corresponds to the 12 M_⊙ with Z = 0.007. Different kinds of points are used for stars with various surface N/C ratios. The labelled stars correspond to objects discussed in the text. The colour map depicts the same division in log(N/C) regimes as the observations going from low (top) to high (bottom) values.