Abstract: The pollen of P.yunnanensis is shed at the four celled stage in March. The pollen germinated at the top of nucellar tissue, then the pollen tube grew into thc nucellar tissue and the tube nucleus into the pollen tube. In the second year, the resting pollen tube revives its activity in the nucellus towards the March. The two unequal male gamete formed in the April. Surro-unding the male nuclei some starch grains were observed. The pollen incubated in the medium containing sucrose grew much slower than that in BKBM-WS.The pollen tube and pollen grains contained abundent starch grains.

Key words: Pinus yunanensis