| Abstract: | The pollen morphology of Cephalotaxaceae was examined with LM,SEM and TEM. Pollen grains in this family are spheroidal or subspheroidal,rounded in polar view, but usually wrinkled with irregular shape. Pollen size is22.6- 34.8 μm in diameter. There is a distinct or indistinct tenuity on distal face.The tenuity occasionally slightly rises above the outline of pollen grains, but oftensukened. Exine rather thin, 1—1.5μm thick, layers obscure, surface of pollengrains is nearly psilate or weakly granulate. Under SEM exine is covered withfine and dense granules, and sparse Ubisch bodies are found on the granular layer. The Ubisch bodies are provided with minute gemmate processes on the surface.Acorrding to our observation under TEM, exine consists of ectexine and lamellateendexine, with the former divided into outer ectexine of granules densely arrangedand inner ectexine of loosely arranged microgranules. Granules of the outerectexine are relatively thick, and connected with each other, forming a structurejust like tectum or separate from each other. Microgranules of the inner ectexineare distinct or indistinct. Endexine is provided with 5- 7 lamellae. As far as information of pollen morphology is concerned, Cephalotaxus oliveriis rather special in the Cephalotaxaceae. First, the tenuity in pollen grains occupies one half of the distal part, much larger than that of the other species in thefamily. Second, the ectexine in Cephalotaxus oliveri may be divided into two distinct layers, outer ectexine and inner ectexine. The former is made of a layer ofsporopollenin masses, which are connected with each other to form tectumlikestructure, while the latter consists of a layer of loosely arranged granules or smallsegments of sporopollenin. The inner ectexine is different from that of other speciesby having a thicker layer of sporopollenin granules. Based on these two features,we support the division of Cephalotaxus into two Sections, Sect. Pectinatae andSect. Cephalotaxus. Pollen grains of Cephalotaxaceae are similar to those of the Taxaceae inhaving spheroidal shape and the tenuity on its distal face. These characteristicsstrengthen the evidence for a close relationship between the Cephalotaxaceae andTaxaceae. Although pollen grains of the Cephalotaxaceae and Taxaceae are similarin some characteristics, they have obvious differences in , for example, size oftenuity, the fine structure of Ulbisch bodies and of the outer and inner ectexine.On the basis of pollen morphology, the present author considers theCephalotaxaceae slightly more primitive than the Taxaceae. |
