On the structure of conidia of Cochliobolus miyabeanus.

Abstract

1. The so-called “septa” that were seen in the fresh conidia of Helminthosporium oryzae (Perfect stage: Cochliobolus miyabeanus) have entirely varished, when observed soon after germination. Each component cell of the conidia rounded up into a spherical body, linked together forming a necklacelike chain. Before germination, these spherical bodies fill completely the integument of conidia, and the area of contact of two bodies gives an optical appearance of cross wall. In this respect the present fungus resembles that of Cercospora beticola and Septoria apii-graveolentis, as reported by Frandsen (1955) and MacMillan et al. (1942) respectively.2. Later, the chain of spherical bodies are in most cases severed into two fragments, generally at the central part. The bodies in a chain are tied to each other with slender connectors.3. As germination advances, the spherieal bodies, one by one from the innermost in the chain, lose their contents and become vacant, apparently sending nutrients to the germ tube.4. When conidia are cut or pressed, the spherical bodies are often separated from the chain. The disjunct single bodies, thus split out of the conidial integument, are still able to germinate.5. Lining the chitinous, brown integument of the conidium a colorless, non-chitinous membrane is oberved. This inner membrane is dissoluble in chloral hydrate solution.6. Shrivelled conidia, not only old viable ones but also those killed with alcohol, could expand in water or with expired air. The expansibility seems to be due to the nature of the inner membrane of the conidia.