There are two Sweet Lemons that I am aware of, perhaps more. I used to have a sweet lemon tree, but have forgot what variety I had. One Sweet Lemon variety is called Dorshapo. It originated in Bahia, Brazil and first came to the USA in 1914. This Sweet Lemon variety is known in Portuguese as the "Lima Doce". Careful study has found the Dorshapo to be a true lemon (acidless). Millsweet Lemon (perhaps the variety I once had), was introduced into the USA by the Catholic padres from Mexico during the old California missions period. - Millet