ULTRASTRUCTURAL STUDIES OF RESTING SPORE DEVELOPMENT IN POLYMYXA-GRAMINIS

Transmission electron microscopy was used to study the development and structure of resting spores and sporosori of Polymyxa graminis. Osmio philic bodies generally distributed in the cytoplasm moved to the peri phery as spores matured. The spore wall consisted of four or five laye rs, two of which extended into spines linking adjacent spores. An unst ained plug in the wall, faced towards the outside of the sporosorus. S ome spores germinated in situ by producing primary zoospores. Bundle-l ike structures in some spores may have been barley yellow mosaic virus particles.