Bava Batra

till I adduced the dictum of Rab Judah: 'A strip of land over which the public has established a right of way must not be obstructed.'  After he [R. Papa] had left him, he [R. Huna] said: Why did I not answer him, '[The prescriptive right of a tree is only]  within sixteen cubits [from the trunk].  [but I am cutting at a distance of]  more than sixteen cubits'? IF HE DIGS A PIT, DITCH OR CAVE HE CAN CUT RIGHT DOWN [TO ANY DEPTH] AND THE WOOD BELONGS TO HIM. Jacob of Hadayab  put the question to R. Hisda: To whom does the wood belong? — He replied: We [can] learn the answer [from the following Mishnah]: If the roots of a tree belonging to a layman spread into a field belonging to the Sanctuary, they may not be used [by a layman], but their use does not involve a trespass.  If now you say that the roots follow the tree, then there is a good reason why the use of them does not involve a trespass. But if you say that they take their character from the soil in which they are found, why is a trespass not involved? — What then [will you conclude] — that the tree is the decisive factor?  [If so], let us see what follows:  If the roots of a tree belonging to the Sanctuary spread into the field of a layman, they must not be used, but their use does not involve a trespass. Now if the tree is the decisive factor, why is no trespass involved? In fact, [this Mishnah, I should say,] tells us nothing about the question in hand, because it is concerned with 'a subsequent growth',  and it holds that the law of trespass does not apply to 'subsequent growth'.  Rabina replied that there is no contradiction [although in the first case the tree is the decisive factor and not in the second]. [In the first case we suppose]  the roots to be within sixteen cubits of the tree, [and in the second case]  beyond sixteen cubits from it. 'Ulla said: A tree which is nearer than sixteen cubits to the boundary of a neighbour's field is a robber, and the offering of first fruits should not be brought from it.  From whence does 'Ulla derive this idea? Shall we say from [the following Mishnah] which we learnt: 'If ten shoots are planted at [equal] intervals in a beth se'ah,  then the whole of the beth seah may be ploughed up to New Year [of the Sabbatical year]'?  [This cannot be.] For what is the total area occupied? — Two thousand five hundred cubits. How much is that for each tree? — Two hundred and fifty cubits. Now, this is less than the space mentioned by 'Ulla.  Can it be then from [the following Mishnah] which we learnt: 'If there are in a field three trees belonging to three different men, they can be combined [to place the field in the category of a plantation field],  and the whole