SUMMARYWhen maintained at high pressure (50-75 atm) the rate of violent spore discharge from cultures ofSordaria fimicolaandEntomophthora coronatais not significantly altered, but withSchizophyllum communeit is reduced to a level close to zero. This is consistent with the view that the ballistospores (basidiospores) ofSchizophyllumare discharged by a bubble-bursting mechanism. A bubble at the hilar appendix could hardly be blown against the high pressures used. These experiments support Olive's theory of ballistospore discharge.