According to the Mishnah on today’s daf (=page), if two meal-offerings became mixed together before the kometz – the fistful of flour – was taken to be sacrificed, then the offerings will remain valid as long as it is possible to take the kometzfrom each one separately. If the two offerings were so mixed together that a separate kometz could not be taken from each, then the offerings are invalid.
In the course of discussing this law, the Gemara quotes a baraita that discusses the baking of matzah. According to thebaraita, if the dough that was prepared for baking matzah was mixed with ketzah or sesame or other types of spice, thematzah remains valid for fulfilling the mitzvah of eating matzah on the night of the Pesach seder, since it is simply “flavored matzah.” While the Gemara first suggests that this would even be true in a case where there were more of the spices than there was of the dough, ultimately the Gemara rejects that possibility and concludes that this law is true only if the dough was the majority.
Tosafot raise the question of how the Gemara considered the possibility that the matzah would be valid even is the majority was the spices, and suggests that the Gemara never meant that there actually were more spices than dough, rather it was referring to a situation where there was a clump of spices in one place and that the suggestion was that the person who ate those spices might still fulfill his mitzvah.
The ketzah spice referred to in the Gemara is Nigella Sativa of the Ranunculaceae family, which, in English is variously called fennel flower, nutmeg flower, Roman coriander, blackseed or black caraway. It is an annual plant that reaches a height up to 30 cm. Its blue blossoms flower at the beginning of the Spring, and its seeds are found in a type of capsule. The seeds are very small (with a length of 2-3 cm) and almost triangular in shape; in a single gram there are up to 500 seeds. To this day the plant is used as a spice; in ancient times it was also used for medicinal purposes. Already in Biblical times it was a domesticated plant (see Sefer Yeshayahu 28:25-27).