Demai, Chapter 2, Mishnah 1. In the previous chapter we learned that from the city of Keziv and onward there is no obligation of demai, since that area was not conquered by those who returned from Babylonia and is not considered part of Eretz Yisrael for this purpose. Our Mishnah teaches the opposite side of the coin: there are fruits that are subject to demai even outside Eretz Yisrael, because they are recognizable and identified as coming from Eretz Yisrael - they did not grow there, but grew in Eretz Yisrael and were brought from there. In contrast, there are fruits whose origin outside the Land is clear, and they are therefore exempt, and there are fruits whose origin is in doubt.
"Eilu devarim mis'asrin demai b'chol makom" - these are the items that are tithed as demai everywhere, even outside Eretz Yisrael:
"Hadvelah" - a cake of pressed figs.
"V'hatemarim" - not dates in general, but a particular type of date found only in Eretz Yisrael.
"V'hecharuvin" - a special type of carob, found only in Eretz Yisrael.
"V'ha'orez" - an especially white type of rice, which comes from Eretz Yisrael.
"V'hakamon" - cumin, a spice they would regularly use to season bread, of a special type that grows in Eretz Yisrael.
With each of these fruits, even when purchased outside Eretz Yisrael, one can determine with certainty that it came from Eretz Yisrael, and therefore it is obligated in demai.
"Ha'orez shebechutzah la'aretz, kol hamishtamesh mimenu patur" - rice that is from outside the Land, whoever uses it is exempt:
That very same type of rice, when it grew outside Eretz Yisrael, is exempt from demai even when it is located in Eretz Yisrael. The reason: it is recognizable that it came from outside the Land and was merely sold in Eretz Yisrael, and therefore it is not obligated in demai.
It is worth noting the precise wording of the Mishnah, which mentioned rice alone. From here we learn that the other fruits - the fig cake, the dates, the carobs and the cumin - when they come from outside the Land, are obligated in demai even while they are in Eretz Yisrael. The reason for this: there are similar types of them that come from Eretz Yisrael, and because of this they are liable to be confused with those that grew in Eretz Yisrael. Because of this doubt of confusion they are obligated in demai, even though their origin is outside the Land.
In summary: our Mishnah teaches that the obligation of demai does not depend on the place of sale but on the identification of the place of growth. Five fruits - fig cake, dates, carobs, rice and cumin - are recognizable as coming from Eretz Yisrael, and therefore they are tithed as demai everywhere. Rice that grew outside the Land is exempt even in Eretz Yisrael, since its origin is recognizable; and from the precise wording of the Mishnah we learned that the other fruits that come from outside the Land are obligated, because of the concern that they will be confused with the fruits of Eretz Yisrael.