Light micrograph of a living epiphytic colonial diatom, Licmophora flabellata, arranged in bunches on the ends of mucilage stalks. Freshwater diatom are unicellular algae with a distinctive silica-based cell wall or skeleton that attach to filamentous algae and leaves. They are found in huge numbers in plankton and play an important role in marine and freshwater food chains. Magnification: x80 at 35mm film size.