A revision of Clematis sect. Tubulosae (Ranunculaceae)

Clematis sect. Tubulosae is revised in this paper. Nine species, two varieties, and three forms are recognized and classified into two subsections. An identification key is provided, and each species is described and illustrated. Brief taxonomic history is given, along with a summary of pollen morphology and geographical distribution. The relationships among the infrasectional groups are also discussed: Subsect. Pinnatae, characterized by its scandent habit, bisexual flowers, white or pinkish, at length spreading, obovate-oblong sepals, and tricolpate pollen, is regarded as the more primitive group, whereas subsect. Tubulosae, characterized by its erect habit, usually polygamous flowers, blue or purple, erect, usually narrowly oblong sepals, and usually pantoporate pollen, is regarded as the more advanced group of the section. Subsect. Pinnatae is believed to have originated from sect. Clematis in Central or East China, and subsect. Tubulosae might be derived from subsect. Pinnatae.