(R' Yochanan ben Nuri): "Keramis'' is obligated in challah as it can become matzah and Chametz. Rabanan say that it cannot. (See Bavli Pesachim 35a - Keramis is rye grass that is found among poppies.)

Question: Why not test it?

Answer: They disagree over the results of the test that were done. R' Yochanan said that they tested it and discovered that it can become matzah and Chametz. The Rabanan said that they tested it and discovered that it did not.

(Mishnah in Terumos): If a Terumah apple was crushed and added to a dough and it became leaven, the dough is prohibited to non-Kohanim. If barley fell into a pit of water, even though the water became rotten, it is permitted (prohibited - according to the text of the Korban ha'Edah). R' Yosa taught that the dough is permitted.

R' Acha/ R' Abahu quoting R' Yosa bar Chanina: They disagree when the juice of the apple caused the dough to rise, but if the flesh of the apple caused it to rise, all agree that the dough is permitted.

R' Yosi follows his opinion - just as over there (in Maseches Shabbos concerning cracking an egg into a cloth heated by the sun) R' Yosi permits it as it is not a full act of cooking; so too here, it is does not fully cause the dough to rise.

(Beraisa): An unripe fig that was hidden in straw and a cake that was insulated in coals - if some of them are uncovered, they may be taken on Shabbos; if not they may not be taken. (Note: According to the Korban ha'Edah and others, the text should not include this Beraisa).