Trillium to a resurrected Trilliaceae. In 1850, German botanist Carl Sigismund Kunth segregated Trillium govanianum into genus Trillidium. Some authorities consider Trillidium to be a synonym for Trillium , while others recognize the taxon Trillidium govanianum based on morphological differences (with other Trillium species) and molecular evidence. Still others support the segregation of Trillium undulatum into genus Trillidium alongside Trillidium govanianum. Infrageneric taxa All names used in this section are taken from the International Plant Names Index. , Plants of the World Online (POWO) accepts 49 species and 5 named hybrids, all of which are listed below. The geographical locations are taken from POWO and the Flora of North America, except where noted. Subgenera The Trillium genus has traditionally been divided into two subgenera, Trillium subgenus Trillium and Trillium subgenus Sessilium, based on whether the flowers are pedicellate or sessile with respect to their attachment to the apex of the scape. The former is considered the more primitive group. Until recently the sessile-flowered subgenus was known by the name Phyllantherum, but the name Sessilium has precedence and should be used instead. has been shown to be a monophyletic group by molecular systematics but its segregation renders the remaining paraphyletic. In 1830, Rafinesque placed Trillium catesbaei into subgenus Delostylium. Since then Trillium persistens and all members of the Trillium pusillum species complex (including Trillium georgianum and Trillium texanum) have been added to this subgenus, which has been shown to be monophyletic. Members of are distinguished from other pedicellate-flowered trilliums by the presence of a definite style. The word Delostylium means "with a small but conspicuous style". Phylogenetic analysis confirms the monophyly of Trillidium and supports the inclusion of Trillium undulatum into that genus. Excluding Trillium govanianum and Trillium undulatum from the analysis, genus Trillium can be separated into four major lineages: Erectum group (15 species) Grandiflorum group (3 species) Trillium Trillium Since all four species groups are monophyletic, this leads to a four-part concept of Trillium that sharply contrasts with the traditional pedicellate vs. sessile dichotomy outlined previously. Erectum group This group of species has pedicellate flowers (on a short stalk) with three separate stigmas (no style) and solid green leaves (not mottled). Species in this group are distributed across North America and Asia, as indicated below. Hybrids are common within this group (the only group of pedicellate-flowered trilliums with natural hybrids). Trillium apetalon – Japan, Kuril Islands, E Russia (Sakhalin)