Abstract: To elucidate taxonomic relationships among the families of Pentapylacaceae,Sladeniaceae and Theaceae,pollen grains of genera,ca.20 species representing three families stated above were examined by light,scanning electron,and transmission electron microscopes.The comparison of pollen morphology shows that the pollen grains of Sladeniaceae are very similar to those.Their pollen grains are oblate to nearly spheroidal and 3- solporate,from rugulate to rugulate -reticulate sculptures and exine structure consisting of thick tectum and columellae,and thin endexine. Howere,the pollen grains of Pentapylacaceae are different relatively from those of Theaceae for having nearly psilate pollen surface and exine structure consising of thin recum,undeveloed columellae and thick endexine though the pollen shape (oblate) and aperture (3-colporate ) are similar to those of Theaceae.As far as the pollen sculpture and exine structure are concerned ,Pentaphylacaceae is more similar to Clematoclethra Maxim. of Actinidiaceae than of Theaceae.

Key words: Pollen exine ultrastructure, Pentapylacaceae, Sladeniaceae, Theaceae.

摘要： 借助光学显微镜、扫描电镜和透射电镜对五列木科Pentaphylacaceae和肋果茶科 Sladeni－aceae花粉进行了观察，并与山茶科Theaceae若干属的花粉进行了详细的比较，同时参考了猕猴桃科Actinidiaceae的花粉特征。研究表明，肋果茶科的花粉与山茶科的花粉具有较多的相似性，如其形状和大小与山茶科中厚皮香亚科的几乎一致；而花粉的表面纹饰（粗糙至模糊的皱波状纹饰）则与山茶属，Freziera属和厚皮香亚科部分属的花粉纹饰相类似。从花粉外壁的结构看，肋果茶的花粉与石笔本属和山茶属的更接近，表现为：花粉外壁层次分化明显，复盖层和柱状层均较厚，外壁内层薄。而五列本科花粉除了形状和萌发孔类型与山茶科的相似外，其纹饰特征和外壁结构均与山茶科的差异较大，如五列本科花粉表面近光滑，外壁覆盖层较簿，柱状层很不发达，外壁内层相对较厚等。抱粉学上认为，肋果茶科与山茶科具有更为密切的关系，五列本科则与山茶科较疏远。支持把肋果茶科作为一个属置于山茶科内或作为山茶科的一个亚科。

关键词: 花粉外壁超微结构, 五列本科, 肋果茶科, 山茶科