Rhododendron ferrugineum L. on dolomitic calcareous soils in the Western Ligurian Alps. — The presence ofRhododendron ferrugineumin some localities of Upper Bormida Valley (Western Liguria) on dolomitic calcareous soils is recorded for the first time. The characteristics of the plant communities in these stations are described and a list of the species found there is given; the main geological, geomorphological and climatic features of the localities are outlined. A particular attention is devoted to the distribution ofRhododendron ferrugineumin Maritimes and Ligurian Alps and to the composition of the plant communities to which it belongs. The author considers that the most important features of the plant communities withRhododendron ferrugineumin Liguria are the following: their occurrence on dolomitic calcareous soils, probably connected with the great amount of humus; their presence at an unusually low altitude and at a short distance from the sea coast, due to numerous ecological factors, particularly to the local conditions of the climate; and their very heterogeneous floristic composition, which can be explained by the shifting downwards of the upper altitudinal belt of vegetation.