Opuntia including antelopes, non-human primates, elephants, birds, and humans. When Carl Linnaeus published "Species Plantarum" in 1753 – the starting point for modern botanical nomenclature – he placed all the species of cactus known to him in one genus, "Cactus". In 1754, the Scottish botanist Philip Miller divided cacti into several genera, including "Opuntia". He distinguished the genus largely on the form of its flowers and fruits. There is considerable variation of taxonomy within "Opuntia" species, resulting in names being created for variants or subtypes within a species, and use of DNA sequencing to define and isolate various species. "Opuntia" hybridizes
Opuntia dulcis Opuntia dulcis Opuntia dulcis has been described as a variety of, and is confused with, "O. phaeacantha". However, "O. dulcis" is a larger plant with ascending branches, to 2 ft (exceptionally 4 ft). While it is a larger plant, immature specimens of O. dulcis may overlap in size with O. phaeacantha. "Opuntia dulcis" resembles "O. engelmannii" in some ways but does not become as erect or large as that species. Also, the spines of "O. dulcis" are finer than those of "O. engelmannii". "O. dulcis" is found across the deserts of the southwestern United States and northern Mexico. It is