Scanning Electron Microscope Studies on Ascospores of Homothallic Species of Neurospora

SUMMARY

The surface and subsurface topography of ascospores of homothallic species of Neurospora has been studied with the scanning electron microscope. Rib surfaces of the ascospore walls, as viewed under SEM, are smooth and free of any fibrillar pattern. Intercostal veins are revealed as pitted furrows in the perisporium aligned with circular to elongate depressions. Height of ribs, depth and continuity of the veins, and distinctiveness of the pitting of the ascospore walls vary according to species. Topographic features of the walls of N. dodgei are the most prominent and those of N. lineolata are the least prominent Surface features of the three other homothallic species fall within these two extremes. SEM views of ascospores after removal of the perisporium show that the germinal pore is an opening in the episporium and that the perisporium is not perforated.