The geology, climate and soils of the Caenlochan N.N.R. are briefly described. The flora is discussed and the results of a primary phytosociological survey are described. One hundred and ninety-three relevés were collected from uniform stands of vegetation and analysed using phytosociological techniques. Thirty-four noda are delimited: 9 of them are heath types, 3 are bogs, 9 are grasslands, 4 represent various types of cliff-ledges and 9 are mires, springs, rills and wet flushes. The floristics and ecology of the noda are briefly discussed.
The ecological and floristic interrelationships among the noda are discussed. An ordination of the noda using constancy data is used to illustrate these relationships and to identify the principal habitat gradients. Soil base-status and soil moisture are seen to be of primary importance but the secondary importance of land-use history in determining the present vegetation is also emphasized.