Abstract: In order to study the cross-compatibility between Lagerstroemia and Lawsonia，Lagerstroemia indica cultivars‘Bicolor’，‘XTSC3’and Lagerstroemia caudata were used to cross with Lawsonia inermis respectively. Then pollen shape and stigma form of both parents，as well as pollen tube behavior after pollination were observed. Results indicated that the pre-fertilization barriers caused the sterility of the distant crosses between Lagerstroemia and Lawsonia. Although pollens of Lawsonia inermis were able to germinate on the stigma of any female parents that were used，pollen tube elongating was hindered，which lead to the failure of fertilization in 72 to 96 h after pollination. The incompatibility，when Lawsonia inermis acted as the female parent，was due to the mismatch of pollen shape and stigma form. Moreover，only a small amount of pollens were adhered on the stigma and the germinations were impeded by callose depositon.

Key words: Lagerstroemia indica, Lagerstroemia caudata, Lawsonia inermis, intergeneric hybridization, incompatibility, pollen germination