Normal experiment methods and electron microscope scanning technique were used to compare the differences of the seed morphological characteristics and microstructure of the seed coats between Pinus sibirica and P. koraiensis . The purpose of this study is to clarify the dormancy and germination characteristics and mechanism of the seeds of P. sibirica. The results showed that the thousand\|grain weight of the measured seeds of P. sibirica was only 39 9% and 48 5% of that of P. koraiensis. The weight of outer seed coats of P. sibirica was 54 04% and 52 6% of their whole seed weight, which was lighter than that of P. koraiensis, while the weight of the seed coat of P. koraiensis was of 61 7% of their whole seed weight. Five layers were seen at the cross section of the hard seed coat of P. koraiensis under scanning electron microscope: external seed epidermis layer (external seed coat), epidermis layer, dense lithocyte layer, palisade layer and inner epidermis. There were four layers in the seed coat of P. sibirica : the external epidermis layer, epidermis layer, palisade layer, and inner epidermis. Thickness of outer seed coat of P. sibirica and P. koraiensis was 400 μm and 1 200～1 300 μm respectively. All these characteristics showed a big hindrance and the permeability barrier in the seed coat of P. sibirica, but not stronger than that of P. koraiensis.
