(Mishnah): A vineyard that was (partially) cleared, if there are still ten vines spread out within a Beis Seah and they are planted legally (meaning in the correct arrangement for a vineyard), it's called a poor vineyard. If a vineyard was planted in an irregular way, if it has an arrangement of two opposite three vines, it's a vineyard.

(R. Meir): Since it appears like a vineyard, it's a vineyard.

(Gemara) (R. Yochanan): A Karachas HeKerem and a Kerem She'charav (a vineyard that was partially removed) are the same thing, but a Karachas has vines removed from its middle and in a Kerem She'charav, they are removed from all sides.

R. Zeira showed the Chevraya 9 rows of 7 vines. Of the 9 rows, he removed one row and left the next row until 5 rows remain. He then did the same in the other (perpendicular) direction until 4 rows remained.

Twenty vines therefore remained. He then removed two vines from each corner and then one from each side of one of the remaining rows (resulting in an arrangement of one single tail vine (in the middle), then a row of three, a row of five and then another single tail vine in the middle - so that it was arranged as 1-3-5-1.

Ten vines therefore remained, which is the meaning of the Mishnah's teaching, "10 vines within a Beis Seah".

Therefore, in every direction the outermost vine serves as a tail to a group of four vines.

Then, next to each of the four tail vines, we view it as if there is another vine planted there (as was done earlier in Perek 4 Halacha 4 - Menachos 61).

You cannot 'plant' an imaginary vine in the four corners (of the 4 by 5 square), as the outermost vine is a tail for the opposite direction in all four directions and there is no tail for a tail.

This shows that there is no tail for a large vineyard (i.e. there is no additional extension for a large vineyard once it is extended by its four tails and their imaginary pairs).

This answers the question asked by R. Yona on the teaching of R. Yosi bar Zemina in the name of R. Yochanan (see earlier Menachos 61-1(f)(g)), who said that one views it as if there is a third vine planted in the row next to the tail and one then measures 4 Amos from there. R. Yona asked - If there were two 'vineyards' back to back, in an arrangement of 4 and 2 ( .::. ), do we view it as two rows of four (as if an additional vine was planted on each side of the 2 vine row (since we don't know which side is the tail)? From here we say that the answer is yes.

(The Mishnah taught that 10 vines spread out within an area of a Beis Seah are called a 'poor vineyard'. It indicated that they prohibit other species to be planted within the Beis Seah. According to R. Zeira, the 9 rows of 7 vines are spread over an area of 64 by 48 Amos (as the space between one vine and the next is 8 Amos). (A Beis Seah is 50 by 50 Amos = 2500 square Amos. The Gemara now attempts to establish whether an area of 64 by 48 Amos is in fact the same as 50 by 50 Amos (a Beis Seah)...)

Remove 2 Amos (of the extra 14 Amos of the 64 Amos length) and put them here (in a perpendicular direction, to broaden the width of 48 Amos to 50 Amos for 48 Amos of the 64 length). (There is now a section which is 50 by 50 Amos minus an area of 2 by 2 Amos, as well as a section of 12 Amos by 48 Amos)

Take a corner of 2 by 2 Amos of the 12 by 48 Amos section and use it to complete the 50 by 50 Amos area. (The extra area of 12X48 Amos = 576 Amos. Subtracting 2X2 from that = 572 Amos, which is in excess of the 50X50=2500 Amos that is the size of a Beis Seah - i.e. the total should be 2500 and according to R. Zeira, it would come out as 2500+572=3072 square Amos.)

However, since there are no vines planted in the corners, one may subtract an area of 16X16 Amos from each corner, which is 276 square Amos X 4 corners = 1024 square Amos. Therefore, 3072-1024= 2048 square Amos, which is 452 Amos less than the correct amount!

Rather, around the edge of the vineyard one should add 4 Amos on each side (i.e. 8 Amos to its length and 8 Amos to its width) for work access meaning that R. Zeira's total should be 72X56 Amos = 4032 square Amos, rather than 64X48 Amos. At this point, even to remove the area of the 4 corners will be 4032-1024=3008 square Amos which is significantly more (508 Amos) than the 2500 Amos of a Beis Seah! The Gemara continues...