ELECTRON MICROSCOPY OF ULTRATHIN SECTIONS OF SCHIZOSACCHAROMYCES OCTOSPORUS III

Abstract

Sporuiation, ascospore structure, and germination in Schizosaccharomyces octosporus was studied by means cf ultrathin sectioning and electron microscopy. Sperulation is initiated by the formation of a double ascospore membrane around each nucleus. The inner portion of this membrane appears to serve as the structural precursor of the cytoplasmic membrane. The ascospore wall then develops around the ascospore membrane and gradually increases in thickness. Mature and germinating ascospores are surrounded by 2 spore coats, the inner one giving rise to the vegetative cell wall. Germination is initiated by swelling and elongation of the cells with subsequent disruption of the outer spore coat. At this stage vegetative cell division is initiated. Further evidence was found to support the contention that the yeast vacuole is not an integral portion of the nucleus. [long dash]H. B. Naylor.