Abstract: The rbcL gene sequences of six species representing five subfamilies of the Hamamelidaceae and the Platanaceae were determined and used in the phylogenetic analysis on the “lower” Hamamelidae sensu Endress (1989) and its allies newly suggested. Four most parsimonious trees were obtained, all having 893 steps with CI = 0.558 and RI = 0.591. The families Cercidiphyllaceae, Daphniphyllaceae, Hamamelidaceae and Saxifragaceae are closely located, while the relationships among them remain unsolved even if more representatives of the Hamamelidaceae were further added in this parsimony analysis. Our results confirm the phylogenetic trees revealed by Chase et al. (1993) and Soltis et al. (1997), instead of those of Hoot and Crane (1996). Considering the morphological features they share, it is suggested that the Cercidiphyllaceae and Daphniphyllaceae be placed into the Hamamelidales. The relationship between the Platanaceae and the Hamamelidaceae shown in our analysis is not so closed as suggested by the cladistic analyses by using morphological characters only(e.g. Lu et al., 1991), while those among the Platanaceae, Trochodendraceae and Tetracentraceae are close as indicated by this study. The Eupteleaceae falls into the Ranunculales. The Eucommiaceae seems to show closer relationship with the Hamamelidaceae, the “core” family of the “lower” Hamamelidae, than with the other members except the Cercidiphyllaceae. The rbcL gene trees imply that the “lower” Hamamelidae is a heterogeneous group,composed of isolated ancient families.

Key words: The “lower” Hamamelidae, Cercidiphyllaceae, Daphniphyllaceae, Molecular Phylogeny, rbcL gene