Tofieldiaceae
Tofieldiaceae is a family of flowering plants in the monocot order Alismatales. The family is divided into four genera, which together comprise 28 known species (Christenhusz & Byng 2016 ). They are small, herbaceous plants, mostly of arctic and subarctic regions, but a few extend further south, and one genus is endemic to northern South America and Florida. "Tofieldia pusilla" is sometimes grown as an ornamental. William Hudson (1730-1793) named "Tofieldia" for the British botanist Thomas Tofield (1730–1779). The family Tofieldiaceae was erected by Armen Takhtajan in 1995. Molecular phylogenetic studies of DNA sequences have shown it to be the  second diverging clade in Alismatales, after the most basal clade, the family Araceae. Before the segregation of Tofieldiaceae was confirmed by cladistic methods, its genera had usually been assigned to Nartheciaceae, Liliaceae, or Melanthiaceae. Tofieldiaceae is recognized by the Angiosperm Phylogeny Group in their APG III system of plant classification. The circumscription of genera in Tofieldiaceae has been controversial. Many authors do not recognize "Triantha" as a separate genus from "Tofieldia". A few authors have sunk other genera into "Tofieldia" as well. A phylogenetic analysis, based on two nuclear genes and ten chloroplast genes, has confirmed that all five of  the genera are monophyletic and that "Triantha" and "Tofieldia" are close sister taxa. Description. Small herbaceous perennials. Leaves equitant (distichous and overlapping), isobifacial. Inflorescence a raceme. Calyculus present. Tepals free. Fruit a capsule, usually septicidal. Phylogeny. The following phylogenetic tree is based on a DNA paper that was published in 2011, modified to accommodate the transfer of the species in "Isidrogalvia" to "Harperocallis".