Abstract: The ultrastructure and changes after hydration of pollen wall in Liriodendron chinense and L. tulipifera were observated by electron microscope. The results were shown follows: (1) The mature pollen wall consists of six layers which are exine sexine, nexine 1, nexine 2, inline 1, inline 2 and inline 3. (2) During hydration of pollen, new layer (pollen tube preparing layer) is formed be-tween intine 3 and vegetative cell plasma membrane by P-particles and coated vesicle. (3) When pollen germinates, pollen tube wall forms by protruding of part of intine 3 and new layer from germinating aperture. (4) Early stage of pollen tube differentiates into two layerspection outer lay-er which is dark and callose inner layer which is electron transparent.

Key words: Liriodendron