Kilayim, Chapter Five, Mishnah Two
This mishnah deals with a vineyard where the vines have been planted less than four cubits one from the other, which is less than appropriate for a properly structured vineyard.
A vineyard that has been planted with less than four cubits [in between rows of vines]:
Rabbi Shimon says: this is not a vineyard.
But the sages say: it is a vineyard, and we look at the middle [rows] as if they were not there.
According to Rabbi Shimon since there are not four cubits between each vine, they dont constitute a vineyard.
The sages say that we can treat the rows in between the outer rows as if they dont exist and just look at the larger distance separating the outer rows. In this way, if there are more than two rows they will constitute a vineyard because there will be more than four cubits separating them. However, the sages would agree with Rabbi Shimon that if there are only two rows separated by less than four cubits, then there is no vineyard.