Answer (Rav Yosef): I base my ruling (which is like R. Shimon, as we shall see) on the following case.

Version #1 (Rashbam): A case came in front of Rav Yehudah, and he ruled that the buyer receives the land in between, even though they were separated only by the amount needed for an ox and its Kelim (four Amos, like we will explain).

Version #2 (Tosfos): A case came in front of Rav Yehudah, and he ruled that the buyer receives the land in between, because for each pair of trees, the separation was no more than the amount needed for an ox and its Kelim for each tree (i.e. eight Amos).

Rav Yosef: I did not know what is the amount needed for an ox and its Kelim until I heard the Beraisa explaining the following Mishnah.

(Mishnah): One may not plant a tree near another's field, unless there are four Amos in between.

(Beraisa): Four Amos is the area needed to tend to a vineyard.

This teaches that the amount needed for an ox and its Kelim is four Amos.

Question: Rav Yosef also holds like an opinion in that Mishnah! (Why did Abaye say that the Mishnah supports Rav Nachman?)

(Seifa of that Mishnah - R. Meir and R. Shimon): If rows of a vineyard are eight Amos apart, one may seed other things in between.

Answer: The case R. Yehudah brought in the Mishnah supports the first Tana. Presumably, the Halachah follows him.

We understand Rav Yosef's source (to say between four and eight), according to R. Shimon:

R. Shimon says in the Mishnah, eight Amos (or more) is considered too far apart;

We learn what is too close from the following Mishnah.

(Mishnah - R. Shimon): If rows of a vineyard are less than four Amos apart (people do not plant vineyards like this), it is not considered a vineyard;

Chachamim say, we ignore those vines that are too close together, and (if enough trees remain) it is considered a vineyard.

Question: Granted, we understand Rav Nachman's source to say that more than 16 is too sparse, according to Chachamim;

What is his source that less than eight is too dense?

Answer: Presumably, just like the amount that R. Shimon considers too sparse is twice the amount that is too dense, also according to Chachamim.

(Rava himself): The Halachah is, between four and 16 Amos (is the proper spacing).

Support (Beraisa): If one bought trees spaced between four and 16 Amos apart, he acquires land and the trees in between;

Therefore, if a tree dried up or was cut, he may plant another.

If they were less than four or more than 16 Amos apart, or if he bought them one at a time, he does not acquire land nor the trees in between;

Therefore, if a tree dried up or was cut, he may not plant another.

Question (R. Yirmiyah): Do we measure the spacing between the thick part of the trunks or the thin part?

Version #1 - Rashbam - Answer (Rav Gavihah - Mishnah): If one grafts a young vine onto a mature vine, we measure (four Amos, to determine if this joins with other vines to make a vineyard) from the second joint (i.e. from the place of medium thickness).

Version #2 - Tosfos - Answer (Rav Gavihah - Mishnah): If one bends a vine back into the ground, we measure (four Amos) from the base of the second place it leaves the ground (i.e. where it is thick).

Question (R. Yirmiyah): If Reuven bought a tree with shoots that were covered with dirt, and they are more than four Amos apart (so it looks like three trees), what is the law?

Answer (Rav Gavihah - Mishnah - R. Eliezer b'Rebbi Tzadok): If one bends three vines back into the ground, and they grew out again, they (join and) are considered a vineyard only if and they are spaced between four and eight Amos apart. (Also regarding trees, it is like buying three trees, and he acquires land.)

Question #1 (Rav Papa): If Shimon sold two trees in his field and one on the border, what is the law?

Question #2 (Rashbam - If he acquires land in the above case,) if he sold two trees in his field and one (which he owned) in another's field, what is the law?

These questions are not resolved.

Question (Rav Ashi): (Rashbam - If in those cases he acquires,) do the following interrupt between the trees (and therefore, he did not acquire land): a pit; an irrigation ditch; a Reshus ha'Rabim; or a row of date trees?

These questions are not resolved.

Question (Hillel): If a cedar tree grew (afterwards) between the trees, what is the law?

Objection: This is obvious! Since there was no separation when Reuven bought them, he acquired land!

Correction: Rather, if a cedar tree was between the trees (at the time of the sale), what is the law?

Answer (Rebbi): He acquires land.

Question: How must the trees be positioned in order that the buyer acquires land?

Answer #1 (Rav): They are in a line.

Answer #2 (Shmuel): They form a triangle.

Rav would say that all the more so he acquires land if they form a triangle;

Shmuel would say that he does not acquire land if they are in a line.

Question: What is the reason?

Answer: The seller wants the area in between, because it can be sown.

Objection (Rav Hamnuna): If he acquires when they are in a triangle, because the seller cannot sow the area in between, he should also acquire when he buys three prickly shrubs, because the area in between will not be sown!

Answer: Trees are important, so the land between them is included. Shrubs are not important.

(Mishnah): If one sells the head of a large animal, the legs are not included;

If he sells the legs, the head is not included.

If he sells the Kaneh (lung), the liver is not included. If he sells the liver, the Kaneh is not included.

Regarding a small animal, if he sells the head, the legs are included;

If he sells the legs, the head is not included.

If he sells the Kaneh, the liver is included. If he sells the liver, the Kaneh is not included.

There are four laws of (retraction from) a sale. If Reuven sold (what was understood to be) good wheat, and it was found to be bad, the buyer (Shimon) can retract;

If he sold bad wheat, and it was found to be good, Reuven can retract;

If it was found to be like it was understood to be, neither can retract;

In the following cases, either can retract. He sold red wheat, and it was found to be white, or vice-versa. He sold olive wood, and it was found to be sycamore, or vice-versa. He sold wine, and it was found to be vinegar, or vice-versa.