The infrageneric classification of the large, cosmopolitan genus, Clematis (Ranunculaceae), has been based on minor differences in vegetative and inflorescence morphology, along with flower size, shape and color. The most comprehensive global classification recognizes 26 infrageneric taxa, including the sometimes segregated genera Archiclematis, Naravelia and Clematopsis, but many of the 250-300 species are uncertainly placed or unplaced within this system. A more sound basis for classification, based on seedling morphology, reproductive compatibility, and a reevaluation of a number of vegetative and floral characters, was suggested by earlier work. A major feature of a new classification would be the division of at least the bulk of the genus into two subgenera, one exhibiting classical epigeal germination and alternate seedling phyllotaxy, and the other exhibiting a type of hypogeal germination and opposite seedling phyllotaxy. The proposed major divisions of the genus are being tested with a phylogenetic study based on DNA sequence data, which will be expanded as part of the development of a comprehensive new classification. We have so far extracted DNA from 18 taxa broadly representative of the genus and are PCR amplifying the nuclear ribosomal RNA internal spacer and a noncoding region located between the trnT and trnF genes of the chloroplast genome. Preliminary results of that study will be presented.

Key words: classification, Clematis, DNA, infrageneric, Ranunculaceae