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 arenaria strongly deflexed and much shorter. Overall, plants (clumps) of cladodes may be 20–30 cm across and about 4–8 cm tall. Fruits are small, about 2.5 cm. Opuntia arenaria Opuntia arenaria was considered a variety of "O. polyacantha" by many botanists, and is still treated that way in the Flora of North America. However, "O. arenaria" is diploid and "O. polyacantha" is tetraploid. It was described by Engelmann in 1856. "Opuntia arenaria" can grow in soil that is essentially pure sand. It has rhizomes up to 1.5 m long that give rise to above ground shoots with small cladodes that are