strains collected from New Zealand, Russia, and Japan. Although a number of reports have confirmed that eastern North American strains are luminescent, non-luminescent North American strains are also known. In general, the intensity of fungal bioluminescence decreases after exposure to certain contaminants; this sensitivity is being investigated as a means to develop bioluminescence-based biosensors to test the toxicity of polluted soils. Most known luminescent fungi are in the genus Mycena or closely allied genera; this grouping of fungi—known as the "mycenoid lineage"—includes P. stipticus and three other Panellus species. Mycelia The mycelia of this species, grown in laboratory culture, have also been shown to be bioluminescent. Early studies demonstrated that short-wave ultraviolet light (at a wavelength of 280 nm) reversibly inhibited the luminescence of P. stypticus mycelia, while longer wavelength (366 nm) ultraviolet was stimulatory. Further, the fungus exhibited a pronounced diurnal periodicity, and maximum luminescence was noted between 6 and 9 pm, regardless as to whether the mycelial cultures were incubated in continuous light, continuous darkness, or a normal day-night cycle. The mycelia of P. stipticus grown submerged in liquid were non-luminescent, but became luminescent while growing on solid substrata. Dark-grown colonies were luminescent in the center, and light-grown colonies were brightest at the periphery. Other experiments have shown that growth temperature and pH have a significant effect on the level of bioluminescence, optimized at and pH 3–3.5. However, light had a significant effect on mycelial growth but not on bioluminescence, and the optimal light conditions for maximum bioluminescence were total darkness. Fruit bodies Bioluminescent tissue in the mature fruit body is restricted to the edge of the gills (as well as the cross-veins that connect them), the junction of the gills with the stem, and the inrolled cap edge. Distribution of bioluminescence along the gill edge corresponds to the position of the cheilocystidia. Less than 10% of the light emitted from both the young and mature fruit bodies is from other tissues, including the fertile hymenial area and the stem. Fruit body luminescence is highly variable between fruit bodies found on different logs in different environments. Genetics Using techniques of genetic complementation, Macrae paired nonluminescent monocaryons with luminescent ones, and concluded that luminosity in P. stipticus is an inherited character, and governed by a single pair of alleles in which luminosity was dominant over nonluminosity. Luminosity factors were independent of intersterility factors. In 1992, Lingle and colleagues agreed