Formes d'inclusions osmiophiles dans les cellules de Ceratocystis ulmi

Abstract

Osmiophilic inclusions were frequently observed in cells of Ceratocystis ulmi (Buism.) C. Moreau in its hosts and in culture. These inclusions vary in shape, size, or their degree of compactness and are composed of fibrillar material and dense granules that are generally 150 Å in diameter. The inclusions are present in vacuolar areas which often appear to be completely or partially devoid of a membrane. Vacuolar areas may also contain aggregates of a similar texture, which often appear to have connections with nearby cytoplasm. Inclusions and (or) aggregates are often adjoining layers of membranes next to or extending within the vacuole. After thymidine labeling, radioautographic grains were observed over these bodies, thus suggesting the presence of DNA. The possible origin of these inclusions from transforming fungal cytoplasm and their importance in the infection process of Dutch elm disease are discussed. A mimeographed English version of the paper is available from the junior author.