Opuntia lindheimeri lindheimeri" is no exception. Opuntia lindheimeri Opuntia lindheimeri is s cactus which is treated by some botanists as a species separate and distinct from "O. engelmannii". Britton and Rose also considered that "O. lindheimeri" is a stand-alone species as did Engelmann who described it in 1850. The point is not settled, and other botanists accept "O. lindheimeri" as a variety of "O. engelmannii". Whatever their taxonomic relationship, the plants are easily distinguished when grown side-by-side and do not generally overlap in their natural ranges. Almost any large "Opuntia" in TX, NM, or AZ has probably been misidentified or misunderstood over
Opuntia readily between species. This can make classification difficult, yielding a reticulate phylogeny where different species come together in hybridization. Also, not all species listed here may actually belong in this genus, meaning that "Opuntia" is not a monophyletic group. "Opuntia" also has a tendency for polyploidy. The ancestral diploid state was 2n=22, but many species are hexaploid (6n = 66) or octaploid (8n = 88). Chollas, now recognized to belong to the distinct genus "Cylindropuntia", are distinguished by having cylindrical, rather than flattened, stem segments with large barbed spines. The stem joints of several species, notably the jumping cholla ("Cylindropuntia