Wall ultrastructure of Arthroderma vanbreuseghemii ascospores

Ascospore cell wall formation in Arthroderma vanbreuseghemii was investigated ultrastructurally by the freeze substitution method. Using this procedure it was confirmed that the mature ascospore cell wall consisted of an inner electron-translucent layer and an outer electron-dense layer, both of which originated as precipitates of electron-dense granules between the double membrane system of the ascospore initial. The outer wall layer showed a mottled appearance between two electron-dense boundaries of different thickness. The boundaries were undetectable with the conventional glutaraldehyde and osmium tetroxide fixation procedure. Wheat germ agglutinin-colloidal gold complex reaction products were detected in the inner layer of the cell wall by a post-embedding method.