This study was carried out to elucidate the physiological and ecological mechamism of the branch pattern and electronmicroscopic structure of photosynthetic organs in Zoysia japonica Steud. The angles between the internodes of rhizome and the branches of Z.iaponica were changed from 0 to 52 degrees. The rhizomes tended to branch from the 3th node to the 10th node. When the terminal bud was damaged by various environmental factors, the initial branching formation was appeared immediately to the 4th node. The internode growth of the rhizome started from the beginning of April and continued to the end of Octobor. It became evident that there is a division labor between two different kinds of photosynthetic cells of mesophyll and bundle sheath tissues in Z.japonica The thick-walled bundle sheath cells surrounds the leaf vascular bundles as the Kranz type and separates them from the mesophyll cells.