Birthlines computed with the Churchwell-Henning accretion rate (Eq. (19)) and the same initial model (Eq. (20)), but with different versions of the code (labelled “original” and “new”) and different values of the fraction f that appears in Eq. (19), f = 1/3 and 1/11. The green dots indicate observations of pre-MS stars (Herbig Ae/Be stars by Alecian et al. 2013, filled squares with error bars; T Tauri stars by Cohen & Kuhi 1979, empty squares). The black short-dashed line is the ZAMS of Ekström et al. (2012), with a few masses indicated, and the black dotted straight lines are iso-radius of indicated values. The final mass of each model is indicated at the end of the corresponding track.