Gemara

(Mishnah): If Reuven accepted to work on Shimon's Beis ha'Shelachin (a field that must be irrigated from a spring) or Beis ha'Ilan (a field with a tree, which is profitable for the worker), and the well dried up or the tree was cut down, he does not deduct from the agreed rental;

If Reuven said 'Chakor (rent, for a fixed amount of Peros each year) to me this Beis ha'Shelachin or Beis ha'Ilan', he deducts from the agreed rental.

Question: Why can't Shimon say 'that is just their name. The rental was not contingent on the spring or tree!'?

(Beraisa): If Reuven said to Shimon 'I sell to you a vineyard', if people call it a vineyard', the sale stands, even if has no vines. This is because he sold a field called a vineyard;

Here also, he should be able to say that it is only called a Beis ha'Shelachin or Beis ha'Ilan!

Answer #1 (Shmuel): When the seller (or owner) calls it so, he can say 'it is just called that.' When the buyer (or renter or worker) calls it so, he bases the sale (or rental) on this.

Answer #2 (Ravina): In the Mishnah and Beraisa, the owner called it so. In our Mishnah, he said 'this Beis ha'Shelachin.' They were standing in it, so he did not need to say 'Beis ha'Shelachin' to identify it. Rather, he called it a Beis ha'Shelachin to make the rental contingent on the spring.

Rishonim

Rif and Rosh (9:2): The Halachah follows Ravina.

Nimukei Yosef (Reish 61a): The entire Mishnah is when the owner told the renter 'rent from me.' Even though it says 'rent to me', it means 'rent from me.' This is a difficult way to explain the Mishnah. The Ran infers that Ravina was forced to explain this way because he holds that when the renter speaks, in every case he is particular.

Rambam (Hilchos Sechirus 8:4): If Shimon was standing in the field and said to Reuven 'I rent this Beis ha'Shelachin or Beis ha'Ilan to you', and the spring dried up or the tree was cut, he deducts from the rental. Since he was standing in it, and did not say 'this', it is as if he said 'I rent it to you like it is now.' Therefore, if he was standing in the field and said 'I rent a Beis ha'Shelachin or Beis ha'Ilan to you', and the spring dried up or the tree was cut, he does not deduct from the rental.

Magid Mishneh: The Rambam rules like Ravina, and is not concerned for Shmuel. He holds that it does not matter whether the owner or renter spoke; if not, he would have specified. The Ramban and Rashba say that Ravina admits that when the renter spoke, he is particular even if he is not standing in the field. The Tosefta supports this.

Rosh: Some say that Ravina discusses only when the owner said so, but if the renter said so, he is particular (the rental is contingent on being a Beis ha'Shelachin) even if they were not standing in it. They infer from the fact that he did not say 'it does not depend on who calls it so.' This is wrong. The Mishnah says that the renter said so, yet he is particular only because they were in the field! Rather, even when the renter says so, he is particular only in this case. Why didn't Ravina say 'it does not depend on who calls it so'? Since Shmuel said that he is particular only when the renter said so, therefore, Ravina teaches that sometimes he is particular even when the renter said so. We say that he deducts from the rental, and do not obligate Shimon to supply a Beis ha'Shelachin, because he said this Beis ha'Shelachin. Had the renter said 'I rent from you a Beis ha'Shelachin, Shimon would need to supply another Beis ha'Shelachin or dig a well or (regarding Beis ha'Ilan) plant another tree. A Tosefta says so.

Question (Piplulei Charifta 3): If he said a Beis ha'Shelachin, according to Ravina he was not particular! I do not know how to answer this.

Answer #1 (Tiferes Shmuel 1): The Rosh does not hold like the Tosefta, which holds that when the renter specified, he is particular even if he said a, like Shmuel. Alternatively, he holds like the Tosefta, that we are not concerned lest he means that it is just called this. The Rosh merely brings the Tosefta to prove that there is a difference between this and a. This is like an owner who rented his house, and it fell. If he said 'this' house, he need not supply another. This is relevant to us (who rule like Ravina) if he explicitly said 'I rent a Beis ha'Shelachin that has a spring' or 'a field that is a Beis ha'Shelachin.' The Tur says that the Rosh is unlike the Tosefta; this is wrong.

Answer #2 (Gra CM 321:10): The Nimukei Yosef says that even though it says 'rent to me', it means 'rent from me.'

Rosh: The Yerushalmi says that the Mishnah is when all the trees were cut, but if there remain trees spaced like 10 in a Beis Se'ah (2500 square Amos), he can say 'the first ones were weak, and crowded the good trees, and they would not have produced much. Now, the trees are spaced out, and they will produce much. The Mishnah is when the spring totally dried up, but if the water was two Amos below ground level, and now it is three, he can say 'bend lower, and it will suffice.'

Poskim

Shulchan Aruch (CM 321:2): If Shimon was standing in the field and said 'I rent this Beis ha'Shelachin or Beis ha'Ilan to you', and the spring dried up or the tree was cut, Reuven deducts from the rental. Since he was standing in it, and did not say 'this', it is as if he said 'I rent it to you like it is now.'

SMA (8): Even if he was not standing in the field, rather, outside, and said 'I rent this Beis ha'Shelachin to you', he is particular. Surely, this is why he said 'Beis ha'Shelachin'. When he is in the field, he need not say 'this'; as long as he mentioned Beis ha'Shelachin, he was particular.

Rema: Some say that this is only if the trees were cut and the trees that remained were spaced less densely than trees spaced like 10 in a Beis Se'ah, and when the spring totally dried up, but if there remained 10 trees per Beis Se'ah, or the spring did not totally dry up, he does not deduct.

SMA (9): If this many remain, it is still called a Beis ha'Ilan. Also, now that the trees are more spaced out, they will grow more Peros.

Beis Yosef (DH u'Mah she'Chosav ba'Meh): The Rif and Rambam omitted the Yerushalmi. Seemingly, they hold that the Halachah does not follow it. However, I say that they omitted because it is obvious. 'Dried up' and 'cut' connotes that the river totally dried and all the trees were cut. It seems that the Magid Mishneh holds like this, for he brought the Yerushalmi in his Perush on the Rambam. However, if so one should not deduct when less than 10 trees per Beis Se'ah remain, unless all the trees were cut!

Shulchan Aruch (ibid): Therefore, if he was not standing in the field and said 'I rent a Beis ha'Shelachin or Beis ha'Ilan to you', and the spring dried up or the tree was cut, he does not deduct from the rental.

Rema: Some say that this is only when the owner said so, but if the renter said so, he deducts even if he is not standing in it.

Taz (DH Machkir): The owner does not seek the renter's benefit. Surely, he merely calls it so! The renter surely means 'like it is now.' See what I wrote in Siman 341:7 (DH Sho'alo, that if an expression is ambiguous, we assume that the one who said it intended for his own benefit).

Gra (11): The Nimukei Yosef and Magid Mishneh merely said that the owner must supply another. They agree with the Rosh that the renter does not deduct! However, the Tur cites the Ramah to say like the Rema.

Shulchan Aruch (154:27): If two brothers divided a Chatzer, and one received an Achsadra (a house with less than four walls) and the other received a garden next to it, he may build a wall in front of the other's windows, but he cannot demand that he close his windows.

Rema: Some say that he can demand that he close his windows.

Shach (28): If Reuven said first 'I will take the Achsadra, and you will take the garden (and Shimon agreed), Reuven has rights to windows. The Gemara discusses when they say to each other, or when Shimon said so to Reuven. The Nimukei Yosef says so in the name of the Ran. This is like they say regarding rental; the Rosh and Tosfos disagree.