PLANT root meristems are a readily available source of mitotic cells which are ideal for cytological examination on account of their large size, high mitotic index and, in selected cases, small number of fairly large chromosomes. The root tip, in which the meristem is found, can be easily handled for experimental studies such as those on the uptake and distribution of phosphorus-32 relative to the mitotic cycle1; or it can be used as a concentrated source of cell components such as nuclei2 or cytoplasmic granules3. In general, the cells are studied after they have been fixed and subjected to some technique designed to render them clearly visible with a microscope. Such methods include embedding and sectioning, or treatment with hot acid, either normal hydrochloric or 45 per cent acetic, to weaken or remove the intercellular cement so that whole cells may be examined separately. Plant mitochondria, however, are extremely delicate and are destroyed by the fat solvents used in the process of embedding in paraffin wax and by the acids employed to remove the intercellular cement. The destruction of the mitochondria allows material which, in life, is localized on these bodies to diffuse about the cell, giving rise to serious artefacts. Thus the diffusion of ascorbic acid on to the chromosomes following the breakdown of the mitochondria has been reported4, and it is likely that other acidic substances, if originally localized on cytoplasmic granules, could be similarly redistributed5.