Reference for Bava Metzia 213:10
אי הכי מאי למימרא לא צריכא דתלי טוניה לחד גיסא ואכתי מאי למימרא מהו דתימא דא"ל פלוג הכי קמ"ל דאמר ליה מאי חזית דפלגת הכי פלוג הכי
And the practice of abutting neighbours is to regard a tree as belonging to the field whither its roots tend. For it has been stated: If a tree stands by the boundary line [between two fields]: Rab said: Whither each is inclined, there it belongs; Samuel said: They share [therein].<span class="x" onmousemove="('comment',' Rashi translates: The tree stands near the boundary, whereon Rab rules that its ownership is fixed by the direction of its roots. Tosaf.: The tree stands actually on the boundary line, the roots spreading equally into both fields, and Rab rules that the ownership is fixed by its branches: it belongs to the field over which they preponderate. ');"><sup>9</sup></span>