Abstract: Exine sculpture of pollen grains is the distinctive and reliable character to classify the two species of Liriodendron L.i.e., L. chinense with foveolate-reticulate sculpture and L. tulipifera with rugulate-verrucate sculpture. According to the evolution of pollen sculpture, the foveolate-reticulate pollen of L. chinense is more primitive than the rugulate-verrucate pollen of L. tulipifera. Ultrastructure of pollen wall shows that the tectate-columellae pollen of Liriodendron is rarer structure type within Magnoliaceae and is more advanced than the atectate type and tectate-granular structural type of most taxa of Magnoliaceae. Palynology supports to treat the genus Liriodendron as a subfamily.

Key words: Liriodendron