Electron microscopy of sporulation in Schwanniomyces alluvius

Sporulation in Schwanniomyces alluvius appeared to be preceded by fusion of a mother and daughter cell. Meiosis probably occurred in the mother cell and one or two spores were formed in the latter. A study of thin sections showed that the spore wall developed from a prospore wall. The mature spore wall consisted of a broad light inner layer and a thinner dark outer layer including warts. An equatorial ledge was present. During germination in the ascus, a new light inner layer was formed and the old layers of the spore wall partly broke up. Ascospores in a strain of S. persoonii had a different wall structure in that the dark layer had changed into light areas separated by dark material which formed bulges at the surface.