We may not separate terumah from [produce of one] species on behalf of [produce which is] not of that species. If one sepa-rated terumah [thus], his terumah is not terumah. All types of wheat are one [species]; all types of fresh figs, dried figs and pressed figs are one [species], and one may separate terumah from one on behalf of the other.  Wherever there is a Kohen [available] one should separate terumah from the superior [produce], but wherever there is no Kohen [available] one should separate terumah from the longer-lasting [produce]. Rabbi Yehudah says: One should always separate terumah from the su-perior [produce].

We should separate as terumah a whole small onion and not half a large onion. Rabbi Yehudah says: It is not so! Rather, [one should separate as terumah] half a large onion. And similarly Rabbi Yehudah was wont to say: We separate the onions of city dwellers as terumah on behalf of the onions of villagers, but not the onions of villagers on behalf of the onions of city dwellers, because [the onions of city dwellers] are food of the nobility.