Gleotrichia echinulata is a familiar fresh water cyanobacterium found in lakes and reservoirs, where its pompon-like colonies can form thick blooms. The photomicrograph presented above was taken with a planapochromatic 25x/0.65 NA objective coupled to an oil-immersion darkfield condenser. Illumination (low wavelength ultraviolet fluorescence) was provided by an HBO 200-watt mercury vapor arc lamp with a UG5 excitation filter. The microscope was a Zeiss Ultraphot III with a automatic 35-millimeter photohead. The film was Fujichrome Velvia. (63x)