Moroccan citron
The Moroccan citron was described by the Moroccan professor Henri Chapot, as being a sweet citron, meaning that its pulp is low in acid. He discovered that the acidity in the more common citrons or lemons, is represented by red on the inner coat of seeds specifically on the chalazal spot, violet pigmentation on the outer side of the flower blossom, and also by the new buds that are reddish-purplish. The Moroccan citron which is acidless is completely lacking the red color. This designation was cited by Herbert John Webber and Leon Dexter Batchelor the editors of the fundamental treatise on citrus, namely The Citrus Industry, which was published by the University of California, Riverside in 1967.
Citrus
The large citrus fruit of today evolved originally from small, edible berries over millions of years. Citrus plants diverged from a common ancestor about 15 million years ago, which was about when it diverged from the closely related severinia, for example the Chinese box orange. About 7 million years ago, citrus plants diverged into two groups, the main citrus genus and the ancestors of the trifoliate orange (poncirus), which is closely enough related that it can still be hybridized with all other citrus. These estimates are made using genetic mapping of plant chloroplasts. A DNA study published in "Nature" in 2018 concludes that citrus trees originated in the foothills of the Himalayas, in the area of Assam (India), western Yunnan (China), and northern Myanmar.