STUDIES ON THE INFECTION PERIOD AND THE INFECTION GATE OF THE CHLAMYDOSPORES OF USTILAGINODEA VIRENE(COOKE)TAK.ON RICE Key factors influencing chlamydospore germination of rice kernel smut FACTORS INFLUENCING GERMINATION OF CHLAMYDOSPORES OF RICE KERNEL SMUT THE CAPACITY OF GERMINATION AND INFECTION OF OVERWINTERED CHLAMYDOSPORES OF USTILAGINOIDEA VIRENS (COOKE) TAK.