the sepals. Dipentodon and Perrottetia are distinctive in that the calyx and corolla are not well differentiated, but resemble each other. Tapiscia and Huertea have a calyx tube and compound, rather than simple leaves. Tapiscia has a uniloculate ovary with a single ovule. Huertea has one locule containing two ovules, or two locules, each containing one ovule. Gerrardina, Dipentodon, and Perrottetia have two ovules in each locule. Tapiscia lacks the nectary disk that is characteristic of the order. Huertea lacks stipules. History Until the first decade of the twenty-first century, the five genera of Huerteales had usually been placed into three unrelated families. Tapiscia and Huertea had long been known to be related. Most authors had placed them in Staphyleaceae and had placed that family in the order Sapindales. Armen Takhtajan established the family Tapisciaceae in 1987 and placed it in Sapindales, but this treatment was not followed by many others and it did not stand up to phylogenetic analysis. Since that time, Staphyleaceae has been recircumscribed. It no longer includes Tapiscia and Huertea and it is in the order Crossosomatales. For most of the twentieth century, Gerrardina and Dipentodon had usually been placed in Flacourtiaceae, a family that is now recognized by only a few taxonomists, and then only as a segregate of Salicaceae.Sue Zmarzty et alii. (in press). "Salicaceae" In: The Families and Genera of Vascular Plants. Springer-Verlag: Berlin;Heidelberg, Germany. Perrottetia, meanwhile, had usually been placed, with considerable doubt, in Celastraceae. Ever since Dipentodon was named in 1911, there had been occasional suggestions that it might be related to Tapiscia and Huertea. In 2001, Alexander Doweld established the order Huerteales, defining it to consist of Tapiscia, Huertea, and Dipentodon. This grouping was later supported by molecular phylogenetic studies. In 2006, a study of DNA sequences showed that Perrottetia was misplaced in Celastrales and that it is sister to Dipentodon in Huerteales. Also in 2006, it was found that Gerrardina'' is a malvid, but its placement within this group remained uncertain. In 2009, Andreas Worberg and co-authors produced the first phylogenetic study that included all of the genera of Huerteales. From one of their data matrices, they derived a well supported phylogeny for the order, as well as strongly supported relationships among the four orders of malvids. Phylogeny The phylogeny shown below is the one found by Worberg and co-authors. Monospecific genera are represented by species names. References External