A Possible Virus Infection in the Green Alga Oedogonium1

SUMMARY Developing germlings of the green alga Oedogonium have been sectioned and some were found to contain particles presumed to be those of a virus. Fully formed particles were hexagonal in a 2‐dimensional section, about 240 nm in diameter with a densely stained surface layer and core; what appear to be different stages in their assembly were also seen. Many of the particles were clustered together in groups surrounded by aggregations of ribosomes. In cells containing many of the particles, the germlings' cytoplasm and organelles showed considerable evidence of disruption and breakdown. These particles have only been detected in germlings, so infection by this presumed virus was probably initiated in the naked, motile zoospore.