Whereas the congregations inside churches seem continually to dwindle, there are, as Dennis (1993) has pointed out, still 'vast congregations of wild plants and animals' inhabiting our churchyards. Many of these are elusive, evident only for a brief time of the day or night or confined to a season of the year. Lichens, on the other hand, in all but the most polluted sites, are ever present, clothing the stonework in a coat of many colours, and yet, ironically, are little known, taken for granted and largely ignored.