Evolutionary tracks for different initial radius R_ini and different initial deuterium content X_D assuming cold accretion (ξ = 0). The solid, dashed, dotted and dot-dashed lines represent the cases R_ini = 0.25,0.5,1.5, and 3 R_⊙, respectively. The colors indicate deuterium content, X_D = 20 ppm (blue) and X_D = 35 ppm (red). The points represent the observed PMS stars in clusters (see Fig. 8). In all cases, stellar masses reach about 0.5 M_⊙ at 3500 K.