Abstract: After a series of seeds of Hopea hainanensis or Vatica astrotricha were treatedunder artificial drying for different days at 25℃ or 20℃,to reduce theirwater content to what this experiment was designed,two groups of thesetreated seeds were used for comparing their vigor and ultrastructural changes of their radicle-tip cells,respectively.The results obtained are summarized as follows: Following that the water content was reduced continuously,the vigorexpressed as GP(germination percent),GI(germination index)and Ⅵ(vigor index)also decreased obivously for these treated seeds in the germination test.And the morpholgy of embryos and their cotylendons changed todarkening and wilting in different extents. For Hopea hainanensis,when its water content was reduced from 34.9%to 25.6% and GP decreased from 65% to 20%,the ultrastructures ofradicle-tip cells showed significant changes: (1) The cytoplasm formed a lot of vesicles,but the fine structure ofnucleus seemed to be normal. (2) The tonoplast ruptured,the structures in the cell became indistinct. (3) The cytoplasm severely segregated with cell wall,nuclear membrane and nucleolus could not be distinguished. When the seed water content was continuously reduced to 20.3% and they had all died,all the structures in the cell were completely destroyed,cytoplasm was disintegrated.Most of substances in some cells had disappeared;and for a great number of cells,there only the cell wall remained. For Vatica astrotricha,its vigor and ultrastructures in radicle-tip cellschanged similarly in the main as Hopea hainanensis.