Introduction

Abstract

Ecological studies of vegetation on old walls has been a much neglected subject judging by the number of papers on this topic. However, the floristics of mural vegetation has been the subject of a number of publications, especially from Italy and France (see 9). One of the first papers to cover some ecological aspects was Richard (1888) on the churches of Poitiers. He posed the question as to how far plants whose principal habitat is the surface of old walls, such as Corydalis lutea and Cheiranthus cheiri, can be considered to be indigenous. Much later Rishbeth (1948) devoted a study to the walls of Cambridge and Woodell & Rossiter (1959) published a paper on walls in Durham. Schmitt (1950) is the author of a popular booklet on a wall as a biotic community.