The document discusses citrus classification, examining various systems proposed by taxonomists for the Genus Citrus based on multiple criteria including plant, leaf, flower, and fruit characteristics. It highlights the complexity of citrus classification since the 19th century, with no universally accepted system due to differing opinions on utility and natural relationships. The classification systems of notable researchers, such as Tanaka and Swingle, are compared, showcasing their differing approaches and the number of species recognized.