Rhobs el Arsa
The Rhobs al Arsa has long been viewed as a citron hybrid, though a different cultivars have been suggested for the parent, for example, Moroccan citron as a male parent and sour orange as the female parent, citron or lemon and a mandarin., or citron and the lime. Detailed genomic analysis has shown Rhobs al Arsa to be highly similar to several cultivars of "Citrus limetta", the limetta or Persian sweet lime, and likely shared a common origin with them, arising from a cross between citron ("Citrus medica") and sour orange ("Citrus" × "aurantium"). The common lemon arose from a distinct hybridization event involving the same two species.
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.