SUMMARYThe existence within the Scottish Highlands of small areas of extreme floristic richness, especially with respect to taxa of northern and montane distribution patterns, is discussed. Possible hypotheses to account for the existence of such areas are considered and the importance of site history is stressed.Falaeoecological studies made at two sites within the Caenlochan N.N.R. are described. On the basis of these studies the past flora, vegetation and probable land-use are reconstructed for the Flandrian (post-glacial) period. Six chronological units are recognized within this period.The inferred floristic and vegetational history is compared with that for other sites. The conclusion is reached that the present rich flora and diverse vegetation of the Caenlochan N.N.R. represents the joint survival from late-glacial times of many montane taxa in a locality peculiarly suited to their needs and relatively undisturbed by man until the recent past.