A simple method for SEM examination of sectioned diatom frustules

We describe an innovative yet straightforward method to obtain high quality thin sections of diatom exoskeletons for observation by scanning electron microscopy (SEM). The use of this new technique allows for clear observatio ns of some ultrastructural valve features, including the raphe, which are g enerally difficult to observe and describe accurately using transmission el ectron microscopy analysis of thin sections or SEM of randomly fractured di atom valves. In addition, because this method involves the complete removal of the organic content of the diatom cells, resulting in clean and mostly undisturbed skeletal thin cross-sections, even the intact valvar structures of weak girdle bands can be studied.