Each segment was teased apart in a sterile petri dish containing 10 ml of sterile water to obtain a suspension of cortical cells. A 50 aliquot of cortical cell suspension was dropped onto l cm block of 1/4 PDA containing 100 g/ml of streptomycin and 50 g/ml of chloramphen-icol in a sterile Petri dish and incubated in the dark at 25%C for 30 days.