Gittin 4: What's Difficult About Being Outside of HaAretz?

We begin with the rabbi's discussion about the agent who brings a get to a wife from a husband who is overseas.  That agent must claim that he witnessed the get being written and being signed.  Why is that so important?  The rabbis consider what it means to be overseas.  Where are the exact boundaries of Eretz Yisrael at that time?  Perhaps cities were too far from HaAretz to have halachic experts living there, and the get was not written or signed according to halacha.  

One of the rabbis' conversations considers the moving borders of HaAretz at that time.  Each different hegemonya could have leaders who restrict movement to another hegemonya.  

The rabbis also consider the particular errors that might be made when writing the get outside of HaAretz.  One of these is writing the document on something that is still attached to the ground.  The example used is a tree that has not yet be cut from the ground.  If the document is written while still attached, was it also signed while still attached?  

I have not learned about this particular halacha before Masechet Gittin, where it has been mentioned twice within the first two dapim.  It will be interesting to learn more about the implications and reasoning behind this particular halacha.