Grapefruit

The grapefruit of America is first described from the East Indies about the middle part of the eighteenth century, but it was not botanically named until MACFADYBN, who treated it thoroughly in 1830 under the specific name Citrus paradisi MACF. Obtaining information from TUSSAC, the autho r of Flora Antillarum (1808-1827), RISSO and POITEAU named it Citrus pompelmos racemosus in a work published during 1818-1822, as a variety of shaddock. Considering that Citrus decumana is the proper name for shaddock, combinations Citrus decumana paradisi NICHOLLS, and Citrus decumana racemosa ROEMER have been proposed. RICCOBONO, in 1908, rejected the use of racemosa because of it is badly chosen, and renamed it as Citrus decumana Patoniana, but of course such name is untenable. DE GREGORIO used Pampelmos for grapefruit as the name of varietal rank, and LELONG presented the name Pomelanus also as variety, claiming that it was adopted from WILLDENOW. Overlooking all of these early nomenclatures, MERRILL and LEE again named graphfruit as Citrus maxima uvacarpa. Many indifferent authors, beginning with LUNAN (1814), included grapefruit in Citrus decumana without distinguishing it by any varietal name. All of these names, except Citrus paradisi, were determined from conception regarding it a botanical variety of shaddock which was first reported by SLOANE (1707) on its origin of introduction into the West Indies. No one except HUME (according t o an informal remark of his conversation) seems to have maintained th at grapefruit is a good species distinguishable from shaddock. Critical study of the writer, however, brought a conclusion that grapefruit is different from shaddock by many distinct essential characters. The grapefruit calyx is well lobed, much smaller, nearly lacking pubescence; fruit is decidedly yellow-colored, not whitish as in shaddock, well flatten at both ends, occasionally providing crator-like stem-end and areolate apex. Oil cell dots of the rind are small, inuniform, even or concave, and contain oil of distinctive aroma. The segments of grapefruit are regular, rounded at the centre; pulp is very distinctly yellow and aromatic, vesicles are small and anastomosing. Seeds are smaller, lighter colored, not dentiform and usually pointed at ends, and contain well marked poly-embryos. The shaddock fruits, on the contrary, are more rounded at both ends, having large calyx with continuous, broken-cut margin. No typical areola and crator depression are found in shaddock fruit, and the oil cell dots of the rind are always convex and never form foveoli. The segments of shaddock fruit are generally irregular, otherwise with the carpel and much pointed at the centre; pulp is white (often rosy), coarsely grained, firm, not juicy, and less refreshing. The pulp vesicles are large and parallel, occasionally intercrossing in the salmon flesh structure, but scarcely anastomosing. Seeds of shaddock are characterised by large dentiform, wedge-shaped outline with strong striations. Poly-embryony has nevern been observed in shaddock. These remarkable distinctions are worthy of bringing grapefruit into the species rank separate from shaddock. Such species is to be defined as a horicultural species, and it is nearly clear that it was originated by chance seedling, most probably from a shaddock seed. It is therefore concluded that Citrus .paradisi MACF. is correct and valid scientific name of grapefruit, now grown in West Indies, North America, Italy, Taiwan and Japan. (Joint contribution: Horticultural Insfitute, Kyushu Imperial University No. 12, Phytotechnical Institute, Miyazaki College of Agriculture, No. 9.)