I have not written about Gemara for a long time because I have been confused about a certain issue. This is Ula in Bava Batra 26 b -a person that has a tree within 16 amot  [arm's breath] of the boundary if his property with that of his neighbor can not bring first fruits.  The Gemara brings then R. Yochanan who concludes  he can because על מנת כן הנחיל יהושוע את הארץ. The issue that has been bothering me is that this is subject to an argument between Rabbainu Chananel and Tosphot. Tosphot obviously holds that between Ula and R Yochanan there is no doubt that if he bought three trees, he gets 16 amot around them and even more if they extend further. The only issue here is that there is just one tree. But to Rabbainu Chananel the law is not like Ula at all. Not just because of R Yochanan, but also because of R Yosi that one can plant a tree right at the boundary itself.

The actual Gemara brings Ula אמר עולא אילן הסמוך למיצר חבירו ט''ז אמה אינו מביא ביכורים גזלן הוא because of roots the extend that far.