Samples of pollen of three genera (Populus, Pinus, andTypha) which are normally shed at different times during the growing season were placed concurrently in four habitats (a pond, a lake, a swamp, and a bog). Their decomposition was traced through the summer and autumn of two seasons. The study shows that there is considerable variability in fossilization of pollen under identical conditions, and that the decomposition of the same pollen is dependent on the habitat, which affects not only the rate of decomposition but also the processes involved.