Kilayim, Chapter 4, Mishnah 7. This mishnah deals with two rows of vines planted in two separate properties, and with the question of whether they join together to be considered a vineyard.
The text of the mishnah:
"Hanotei shurah achas b'soch shelo" - one row of vines (whether a row of three or a row of two and three) is planted in his own ground.
"V'shurah achas b'soch shel chaveiro" - the second row is planted in his neighbor's ground.
"V'derech hayachid v'derech harabim ba'emtza" - and even though a private path or a public road separates between them.
"V'gader shehu namuch mei'asarah tefachim" - or a fence stands between them, and it is lower than ten tefachim. Ten tefachim is the standard height required for something to be considered a fence and a partition that divides between things, and here its height is less than that.
"Harei eilu mitztarfin" - in each of these cases the two rows join and combine to be considered a vineyard, even though they stand in two properties belonging to two different people, and even though there is a private path, a public path, or a fence lower than ten tefachim between them.
The measurement of a public road:
The commentators explained that the "public road" mentioned here is not a road eight amos wide or more, since once the gap reaches eight amos the two rows of vines do not join, as we will learn further on - the rows must stand within eight amos of each other. Therefore it must be speaking of a narrower road, and in such a case the rows do join.
A fence higher than ten tefachim:
The mishnah continues: "Gavoha mei'asarah tefachim - einan mitztarfin" - when the fence is higher than ten tefachim the rows do not join, because there is a partition here that separates between the two of them.
"Rabbi Yehudah omer: im irsan milmaalah, harei eilu mitztarfin" - if he took the vines themselves and laid them over the fence, then even if it is ten tefachim high, the two rows of vines on the two sides of the fence join with one another. The reason: by doing so he showed that the partition is not a partition at all and does not truly separate, since he laid the vines across its top and connected the two rows together. Therefore, as a matter of halachah as well, they join to be considered a vineyard.
In summary: in this mishnah we learned that two rows of vines planted in two separate properties join to be considered a vineyard even when a private path or a public road separates between them, or a fence lower than ten tefachim; whereas a fence higher than ten tefachim separates and prevents the joining, unless he trained the vines over its top - for then it turns out that the partition does not separate, and the rows do join.