Ballistospore discharge in Itersonilia perplexans

Ballistospore discharge in Itersonilia perplexans is described. Evidence is presented that a drop of liquid, and not a gas bubble, develops at the hilar appendix immediately before discharge. Spores detached on a micromanipulator needle produce liquid drops. The trajectories of several spores have been plotted. The horizontal and vertical distances of discharge have been measured, and the terminal velocity of sedimentation. From these values, the initial discharge velocity has been estimated at 5.5 m s−1. Evidence is presented that discharged spores carry a negative electrical charge. Two possible mechanisms for spore projection are discussed, a rapid transference of the centre of mass of the spore associated with wetting, and a change in the electrical charge on the spore surface at wetting, followed by electrostatic repulsion.