The study of fossil and living spores (of lichens and mosses) and pollen (of flowering plants); the technique through which the fossil pollen grains and spores from archaeological sites are studied. The examination of their production, dispersal, and applications is an aid to the reconstruction of past vegetation and climates and developing relative chronologies. Each kind of flowering plant produces pollen that is unique and pollen grains have tough coverings that can last a long time. The resilient exine of the pollen and spores is preserved in anaerobic environments, such as lakes and bogs, and some acidic and dry soils, as in caves. Palynology helps archaeologists find out what plant resources were available to ancient peoples and what the climate was at those times. Palynology was developed by Swedish botanist Lennart von Post.