Premain-sequence evolutionary path is understood as follows:
Consider a situation that a star with is left when accretion stops.
Figure 4.22 indicates that
a less-massive star with is fully convective.
Thus, this evolves along the convective Hayashi track (Hayashi 1961)
down to the main-sequence.
In contrast, a massive star with (Fig.4.22)
is fully radiative and evolves
along the radiative Henyey track (Henyey, LeLevier, & Levee 1955) to the main-sequence.
These differences are clearly indicated in Figure 4.24.
We can see veritical Hayashi track is seen essentially for stars with
Massive stars with
evolve to the upper-left direction
along the Henyey track.