Citrus taxonomy
All of these hybrids have in turn been bred back with their parent stocks or with other pure or hybrid citrus to form a broad array of fruits. Naming of these is inconsistent, with some bearing a variant of the name of one of the parents or simply another citrus with superficially-similar fruit, a distinct name, or a portmanteau of ancestral species. The Ponderosa lemon ("Citrus limon" × "medica") and Florentine citron ("Citrus x limonimedica") are both true lemon/citron hybrids, the Bergamot orange is a sweet orange/lemon hybrid and the Oroblanco is a grapefruit/pomelo mix, while tangelos are tangerine (mandarin)/pomelo or mandarin/grapefruit hybrids, orangelos result from grapefruit backcrossed with sweet orange, and a sweet orange backcrossed with a tangerine gives the tangor. One lumia, a member of the sweet lemons, is the product of crossing a lemon with a pomelo/citron hybrid, though another lumia variety, the Pomme d'Adam, is a micrantha/citron cross, like the Key lime. The most common and commercially popular 'limes', the Persian limes, are Key lime/lemon hybrids that combine the genetic lineages of four ancestral citrus species: mandarin, pomelo, citron and micrantha.
Gin and tonic
Gin and tonic is traditionally garnished with a slice or wedge of lime, often slightly squeezed into the drink before being placed in the glass. In most parts of the world lime remains the only usual garnish; however, in the United Kingdom it has become common to use lemon as an alternative fruit; use of both fruit together is known as an "Evans". Although the origins of the use of lemons are unknown, their use dates back at least as far as the late 1930s. In addition lemons are often more readily available, and cheaper to purchase, than limes. The use of lemon or lime is a debated issue - some leading brands, such as Gordon's, Tanqueray, and Bombay Sapphire, recommend the use of lime in their gin.