The fixation of cells of petiolar hairs of tomato was monitored by phase contrast and Nomarski interference contrast microscopy. Because the cuticle covering these hairs is relatively impermeable some fixatives enter only the base of the hair so that a ‘fixation front’ can be followed through a single cell. The basal end of such a cell may be immobilized by the fixative while the apical end is still streaming. A variety of fixatives were tested at room temperature and at 273–278 K. All procedures tested failed to stabilize a pleomorphic canalicular system that is a dominant feature of these cells so that no clue to the presence of this system can be seen in sectioned material. It is therefore very desirable that images of fixed cells be compared to the structure of similar cells which are still alive.