The postformalin ammoniacal silver reaction(ASR) for basic nuclear proteins was applied to the cold-treated interphase nuclei and mitotic chromosomes of Trillium kamtschaticum and observed with the light and electron microscope. Cold-induced negatively heteropyknotic regions of Feulgen stained metaphase chromosomes were not stained by ASR, too. The possible role of histones in cold-induction of negatively heteropyknotic regions was discussed. Electron microscopic analysis of the cold-treated interphase nuclei revealed certain characteristic structure which appeared closely associated, at the same time, with a number of chromatin masses. They consisted, structurally, of a distinct meshwork of convoluted 200-300 Å thick fibrils, less dense than the chromatin. The connections between these structures and the adjacent chromatin masses were apparently established by means of fibrils coming out from the chromatin masses. The morphology of these structures appears to correspond exactly to the 'micropuffs' described by Lafontaine (1965) and Esponda and Gimenez-Martin (1971). It might be deduced from this that the cold-treated chromatin mass gives rise to differentiations similar to the puffs in polytene chromosomes. The relation between cold-induced chromatin activities and cold acclimation of plants was discussed.