is eaten. The halakha (Jewish law) prescribes the minimum amount of maror that should be eaten to fulfil the mitzvah (a kazayis or kezayit, literally meaning the volume of an olive) and the amount of time in which it should be consumed. To fulfil the obligation, the flavour of the maror must be unadulterated by cooking or preservatives, such as being soaked in vinegar. Types of maror The Mishnah specifies five types of bitter herbs eaten on the night of Passover: ḥazzeret (lettuce), ʿuleshīn (endive/chicory), temakha, ḥarḥavina (possibly melilot, or Eryngium creticum), and maror (likely Sonchus oleraceus, sowthistle). The most common vegetables currently used as bitter herbs are horseradish and romaine lettuce. Hazzeret Hazzeret is undoubtedly domestic lettuce. The word is cognate to other Near-Eastern terms for lettuce: the Talmud identifies hazzeret as hassa, similar to the Akkadian hassu and the Arabic hash. Modern varieties of lettuce are only slightly bitter or not at all, such as iceberg lettuce and romaine lettuce. However, in the past domestic lettuce was bitter, and heirloom varieties of lettuce that are bitter are still available to gardeners. Romaine lettuce is the most commonly used variety, perhaps because it still preserves a slight bitter taste. In addition, the Talmud remarks that Romaine lettuce is not initially bitter, but becomes so later on, which is symbolic of the experience of the Jews in Egypt. The "later" bitterness of lettuce refers to fact that lettuce plants become bitter after they "bolt" (flower), a process which occurs naturally when days lengthen or temperatures rise. Wild or prickly lettuce (Lactuca serriola) is listed in Tosefta Pisha as suitable for maror under the name חזרת הגל or חזרת גלין. However, its absence from the approved list in the Mishnah and Talmud indicate that it is not halakhically suitable. `Ulshin The second species listed in the Mishnah is `ulshin, which is a plural to refer to both wild and cultivated types of plants in the genus Cichorium. The term is cognate to other near-eastern terms for endives, such as Aramaic עלת and Arabic `alath. Tamcha The Talmud Yershalmi identified Hebrew tamcha with Greek gingídion, which has been positively identified via the illustration in the Vienna Dioscurides as the wild carrot Daucus gingidium. Rabbi Yom-Tov Lipmann Heller, in his Tosafot Yom-Tov, identified the Mishna's temakha with Yiddish chreyn (horseradish). This identification has long been recognized as problematic, as horseradish does not grow