"Just as a vegetable, its way is to grow on all water" - The reason of the vegetable is explained in the first chapter of Rosh Hashanah (Rosh Hashanah 14a), that it is written "granary and winepress" about tithes: "'Like grain from the granary...' The granary and the winepress are unique because they grow on most water and are tithed according to the previous year, this excludes vegetables which grow on all water [and therefore are not tithed according to the previous year]". Even though tithing vegetables is rabbinic, and how can one make a midrashic category based on a thing that is rabbinic [and not directly from the Torah], the rabbis hooked it on verses, as Rashi explained. But Rabbenu Yitzhak explained: If is not taught about tithe, it is taught about 7th year that is practised for vegetables from the Torah, for the core of the derashah is derived for 7th year for vegetables, that [7th year] is from the Torah whether vegetable or tree, as we say in Rosh Hashanah (Rosh Hashanah 15b): "I say to you tithe of carobs is rabbinic and you say to me 7th year?!", for bushes are from the Torah, and this is true for vegetables also for everything that is unspecified and falls into the category of "He eats and guards" is from the Torah, as we teach in Shevi'it (Mishnah Shevi'it 7:1): "They said a general rule regarding 7th year...". And this is what it [the principle about the difference between vegetables and trees] means [according to R"I]: Just as granary and winepress grow on most water and we go after the previous year with regard to 7th year, so too... Problem [on R"I]: For behold etrog grows on all water as is true in our sugya, and even so we say that it is equal to a tree regarding 7th year that it goes after fruiting! Tentative solution: [What it means] that we go with it after fruiting for 7th year is specifically to make it more stringent, just as if it fruits in the 7th year but was collected in the 8th [but we would never permit the produce based on this]. Alternative solution: Even though etrog grows on all water, we do not separate it from the law of other trees regarding 7th year, for in the cases of orlah and 4th year the Torah does not separate it from other trees. And the derashah of granary and winepress comes for vegetables, not etrog. But regardless, for tithe which is rabbinic, the sages decreed "After its gathering is its tithing" since it grows on all water like a vegetable. [New problem:] But if you say: Why is the etrog not considered to be equal to a tree for kilayim for there is no kilayim in a vineyard, so let [the Mishnah] consider that the etrog is like a tree in 4 ways!? Solution: It only taught that it was equal to a tree with respect to going after fruiting and to a vegetable with respect to going after collecting. [New problem:] If you say: Why did the Mishnah not consider that it is similar to a vegetable in 2 ways, such as with regard to peah, for etrog is not obligated in peah since it is not all gathered at once, and with regard to peah we need all the gathering at once and it is for this reason that we exclude date palms in the chapter Klal Gadol (Shabbat 68a) and in chapter Makom She-Nehegu (Pesahim 56b), and with vegetables also peah is not practised since it is not in the category of "continuing" that is required [for peah] there. Solution: Because there are many trees that are not obligated in peah, such as carobs, taught in Peah (Mishnah Peah 1:5), it was not fitting to teach that it was equal to vegetables [in this, since it is also the same as many trees]. And also for this reason it did not say that it is equal to a vegetable regarding first fruits, since first fruits is only for the 7 species as it says in the Sifrei, and if so [the etrog] would also be similar to other trees.
"[The koy is] neither [similar] to a wild animal nor to a domesticated animal". Explanation: Regarding interbreeding because it is doubtful to us if it is a type of wild or domesticated animal. Rabbenu Eliezer raised a problem: According to the one who says the koy is its own type of animal, what could "It is doubtful to us..." be talking about? Even if we knew that it was a wild animal, we would not interbreed with it because we don't interbreed a ram with a deer! Solution: This could be according to the one who thinks this koy had sex with a sheep or a doe and it is doubtful for us whether we are concerned about the seed of the father or not, for if we say we are not concerned, then we could interbreed it with a deer.
"And a wife with less than something worth a perutah would not let herself be acquired". Rashi's explanation: Because it would be shameful to her, therefore the laws of exchange is not applicable to her in kiddushin, even with an item that is worth a perutah if he gave it to her under the laws of exchange. This was a problem for Rabbenu Tam: For if so, should she spread out her hand and receive it, let her be betrothed with something worth less than a perutah! Another problem: Since the reason depends on "Because it would be shameful to her", if so why doesn't it object in the Gemara regarding "the daughters of Rabbi Yannai that were particular about themselves and would not be betrothed for less than 3 kavs of golden dinars", just as they object later (Kiddushin 11a) on the words of Beit Shammai! Another problem: Since you might think now to learn acquisition of a wife from acquisition of a field, if so a wife could also be acquired through presumption like a field! Another problem: Later (Kiddushin 5a) it asks in the Gemara "How do we know [a wife can be acquired] with a contract?", and what did it ask—it should learn it from the field!? Rabbenu Tam's solution: Our text should read "With something worth less than a perutah she is not acquired", and should not read "let herself (נפשה)", for the matter does not depend on how particular she is, rather this is the reason: Because of the גזירה שוה of "purchase" "purchase" from the field of Efron, for it is written "money", and something worse less than perutah isn't called "money". And that problem which you raised earlier [in the sugya]: "I could say: this too!" it couldn't raise the issue regarding contract or presumption, for it is obvious that we can't learn from [the] "purchase" [ג״ש] to make a wife['s law the same] as all the topics of [purchasing] a field, and this is why later we ask "How do we know with a contract?", for we can only learn from the field for money specifically it is written "purchase". And it only objects from [the laws of] exchange because exchange is similar to biblical "money" when [the item of exchange] is worth a perutah. And this is his explanation [of the flow of the Gemara]: "I could say: this too!" that a wife can be acquired with exchange when the exchange is worth at least a perutah, for this is more similar to biblical "money" than a contract that is worth a perutah, for one does not need to make the contract [i.e. the paper] worth a perutah as we say in Gittin (Gittin 20a) "If he wrote it on something which is forbidden to derive benefit from—[the get is] kosher", but exchange that is worth a perutah is similar to money. And [the Gemara] responds: Exchange can be worth less than a perutah, and if so it would not be really money but rather some other acquisition. [A new problem:] And if you say: How would I think that a woman can be acquired through exchange from the field of Efron, for the field itself was not purchased with exchange since we do not find [that] exchange [is effective] for Gentiles, as we say in Bekhorot (Bekhorot 13a): "Since a Jew has one way of purchasing it [in this case: drawing (משיכה)], so too does a Gentile have one way [money]"! Solution: This [in Bekhorot] wasn't discussing exchange when it said the Gentile has 1 way, and this is what it meant: A Jew has one way of acquiring, except for exchange which is the same for both of them [the Jew and Gentile]. And this is also implied later (Kiddushin 8a) regarding being sold to a Gentile from "'The money of his acquisition (כסף מקנתו)'—with money he can be acquired, but cannot be acquired under the law of grain or items, and what are these? exchange"—we learn from this that other things [i.e. non-slaves] can be acquired through exchange by Gentiles. And so too was Rabbenu Tam accustomed to sending power of attorney documents through Gentiles and they would acquire it through exchange. But regarding this [practice] one needs to be careful that one shouldn't write "And I acquired from him", for there is no power of emissary (שליחות) or ability to benefit (זכיה) for Gentiles, as we say in the [5th] chapter of Bava Metzia (Bava Metzia 71b), but we write "And the Gentile acquired". [New problem:] And if you say: If so, since it is obvious to us that a wife can't be purchased with exchange, why do we need a verse!? (Kiddushin 8a) Say it from "Money of his acquisition", that he can't be acquired under the law of grain or items, which is excluding exchange, for we make a הקיש between Hebrew slave and Hebrew slave girl, for from her we learn later (Kiddushin 14b) that the Hebrew slave can be acquired with money, and the Hebrew slave girl is in a הקיש with the wife, as it is written, "'If he takes another'—Scripture makes a הקיש between her [a slave girl] and another [a wife]" when we derive that both can use a contract to be acquired!? Solution: Inclusions for acquisitions carry through a הקיש [we can learn an inclusion from one category to another, e.g. that the wife can be acquired with a contract], but not exclusions for acquisitions [e.g. that the wife can't be acquired through exchange], for in a similar manner we say in the chapter Kol Ha-Basar (Hullin 117b) "Three verses are written about blood—one to exclude it from notar (leftovers of sacrifices), one to exclude it from me'ilah (misuse of Temple property), one to exclude it from impurity", and in the chapter Beit Shammai (Zevahim 45a) it derives notar [using a הקיש of] "profanation" "profanation" from impurity, and if so why does it need 2 verses, one for notar and one for impurity!? Rather no, it is because the ג״ש of "profanation" is not to be lenient but to be stringent [just like how we can learn that contract is included for a wife but not that exchange is excluded].
