| Abstract: | This paper deals with evolution, classification and pollen morphology of theHamamelidaceae, an important family in phylogeny of angiosperms. I. Pollen morphology and systematics of modern Hamamelidaceae. The pollen morphology of the family may be divided into the following four types: (1) Tricolpate: Hamamelis, Loropetalum, Mytilaria, Corylopsis, Sysopsis, and Distylum etc.;(2) Tricolpate with operculum: Disanthus; (3) Tricolporate: Rhodoleia; (4) Pantoporate:Liquidambar. The tricolpate pollen of the Hamamelidaceae is a primitive type in angiosperms, but themost ancient type is monocolpate pollen. Therefore, the family might have evolved from theMagnoliaceae of the monocolpate pollen. The pantoporate pollen is an evolutionary type inthe family. It might have evolved from the tricolpate pollen. II.The fossil pollen of the Hamamelidaceae 1 .General introduction of the fossil pollen of the family Hamamelidaceae The most’ancient fossil pollen belonging to the family was found in the middle-late Early Cretaceous. Palynologists call the fossil pollen of the Hamamelidaceae Retitricolpites,which consists of three genera: Hamamelis L.,Corylopsis Sieb. et Zucc and FothergillaMurr. Liquidambar is of an advanced type in the fossil pollen of the Hamamelidaceae. Itwas found in the period from the Palaeogene to the Neogene in China. 2. The geological history of the Hamamelidaceae may be divided into the following fourstages: (A) The Early Cretaceous stage or origination stage. The family may be evolved fromMagnoliales in the middle-late Early Cretaceous. (B)the Late Cretaceous stage or formation stage. The family is much developed in the period. (C) The Tertiary stage or development stage. The family was a much developed one among angiosperms. (D)The Neogene tomodern stage or perfection stage. The evolutionary type, the Liquidambar type of theHamamelidaceae, was much developed in the Neogene. III. The palaeopalynological evidence of evolution of the Hamamelidaceae The earliest fossil pollen of angiosperms was found in the Barremian (Early Cretaceous)in England, Israel, the United States of America etc., and was named as Clavatipollenites byCouper (1953). In recent years, Clavatipollenites was also found in the middle-late EarlyCretaceous in Nei Monggol and Jiangxi Province of China. We also found Retitricolpites inthe middle-late Early Cretaceous in Nei Monggol and Jiangxi Province. Retitricolpites, belonging to the Hamamelidaceae, is a primitive type among angiosperms, but it is youngerthan Clavatipollenites. Therefore, the pollen of Hamamelidaceae may have evoloved fromClavatipollenites, which may have evoloved in turn from that of Magnoliales. |
