Citron
There are also a number of citron hybrids; for example, ponderosa lemon, the lumia and rhobs el Arsa are known citron hybrids, some are claiming that even the Florentine citron is not pure citron, but a citron hybrid.
Greek citron
It was also called "pitima", or the "cedro col pigolo" ("citron with a pitom), because its usually persisting pitom (carpel). The last does not only enhance its character, but also adds Halachic promotion.