Number, size, shape and distribution of nuclei in hyphal tip cells of Botrytis cinerea treated with inosine were different from those in the untreated ones. In the presence of inosine, the nuclei increased remarkably, and nuclei which differed in size and shape were contiguous in the hyphal tip cells and in the nuclei with one or two budding-like projections were frequently observed in these cells. In the hyphal tip cells treated with inosine, the nuclei lined up in one parallel or diagonal

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... although the nuclei distributed in a file more or less uniformly in the untreated ones. From electron microscopy of the hyphal tip cells treated or untreated with inosine, the nuclei of various stages in mitosis were observ ed in the untreated ones, while in the treated ones, deformation of the nuclei suggesting non-mitosis, such as budding was frequently observed: nuclei whose part of the nuclear en velope began to project out, formed developing projections or the projections appeared nearly detached from the parent nuclei. In these nuclei, the spindle pole bodies and microtubules, which took roles in mitotic division of nuclei, were not found.