Foliicolous lichens are lichens that grow on the living leaves of angiosperms, fern fonds, phyllodes, phylloclades and young bamboo culms. Generally they occur on the leaves that shed off in 2-5 years or stayed longer (e.g. Agave and palm leaves), except few taxa which were found to grow on annually deciduous leaves. Majority of the foliicolous lichens were found on the upper side of the leaves i.e. epiphyllous, but few also grow on the lower side i.e. hypophyllous. Foliicolous lichens generally prefer growing over leaves of lower branches which not only enjoyed thepartial shade of the over growing branches but also had a more humidenvironment than others. Based on their substrate specificity, they can be divided into three groups: 1) Eufoliicolous lichens: they grow and reproduce entirely on the leaves and have a crustose thallus that is tightly adnate to the substrate. 2) Facultative foliicolous lichens: they usually grow on barks, petioles and twigs but exceptionally on leaves. 3) Pseudofoliicolous (indifferent or ubiquitous) lichens: besides growing on leaves they can grow on different substrates, such as rock, bark, soil etc. The diversity and density of foliicolous lichens isabundant in the tropical rainforests of Central and South America, Africa and Southeast Asia, due to availability of optimum temperature, humidy, sunlight and shade throughout the year. Besides tropical rainforests, they are also reported from subtropical and temperate rainforests having humid areas, but the diversity and density in the subtropical and temperate regions is less in comparison to tropical regions because of lack of suitable macro- and micro- climatic conditions responsible for the luxuriance growth of these lichens.