Direct observation of hymenes in diatoms by low-voltage SEM

From the early days of Kolkwitz and Marsson (1908) diatoms have proved to be valuable in pollution studies, especially of river systems. Economic applications have developed because the remains of sedimentary diatoms were found to be useful for many industrial processes owing to the fine structure and inert nature of the siliceous materials. Their ecological significance arises from observing that diatoms that grew in oceanic and freshwater sediments contain indications of past environmental conditions; more recently, diatoms have been used to detect pH changes attributed to 'acid rain.' The first record of a diatom can be traced back to the early 1700s when an English gentleman looked at roots of the pond-weed Lemna using his simple microscope. Today, extensive studies using TEM and SEM techniques have provided much new information about the fixed and variable details of the diatom, yet research focusing on the morphology of the shell structure remains very active.