The thallic mode of conidiogenesis in the Fungi Imperfecti

摘要

The current developmental concept of the thallic mode of conidiogenesis essentially involves the simple conversion and disarticulation of preexisting hyphal elements, in which extension growth has ceased, into conidia which are delimited by transverse septa. Two kinds of thallic development were originally interpreted from light microscopic investigations. In this paper, holothallic conidium formation, which is demonstrated byGeotricluim candidum, and enterothallic development, which is exemplified bySporendonema purpurascensandBriosia cubispora, are compared and ultrastructural and karyological characteristics of these mechanisms of conidiogenesis are illustrated. Scanning electron microscopic analyses of conidium formation inOidiodendron trancatumandTrichosporon beigeliiand light microscopic investigations ofSympodiellasp. andAmblyosporium spongiosumhave revealed that additional variations exist in the thallic mode of conidium ontogeny. On the basis of these new data, and a consideration of other species of imperfect fungi which demonstrate similar mechanisms of conidiogenesis, a revised concept of thallic development is presented.