SUMMARYMorphological and cytochemical examination of the ascal wall ofTrichobolus zukaliiand its associated mechanism of dehiscence was made. Layering of the ascal wall was enhanced by the stains, Congo red and toluidine blue for light microscopy and by silver methenamine for electron microscopy. At spore liberation a wide operculum is infrequently formed. Ascal dehiscence occurs typically by an irregular rupture of the wall at the apex. The mature ascal wall does not appear to have a distinct apical apparatus. The wall is thinnest at the apex and consists of two layers. Each layer becomes conspicuously stratified toward the base of the ascus. The external region of the outer layer is longitudinally ribbed at the tip.