The morphological nature of the open dichotomous leaf venation ofKingdonia andCircaeaster and its systematic implication

After the further studies on the open dichotomous leaf venation ofKingdonia andCircaeaster, we considered that the venation of these genera is incomparable to that of some gymnosperms such as Ginkgoaceae, and is a degenerated characteristic in the morphological nature. We also considered that this characteristic is very important on determining the systematic relationship between these genera and other members of Ranunculales (sensu Takhtajan 1980), but its implication in the phylogeny of angiosperms was overemphasized. The project was supported by The National Natural Science Foundation of China (No. 39630030) and The Laboratory of Systematic & Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences.