The distribution atlas of pteridophytes and phanerograms of Switzerland (Welten and Sutter 1982) was digitized at the Swiss Federal Institute for Forest, Snow and Landscape Research in Birmensdorf (CH). The data are stored in a relational data base, which is flexible enough to allow any kind of retrieval and analysis. The florestic diversity and its dependence on various factors was analysed by comparing the species number per mapping unit. A relation could be established between species numbers and the following factors: range of altitude covered by the mapping unit, rock type, geographical region, and thoroughness of the mapping. Low species numbers were found in most of the mountains areas in the Ticino consisting mostly of non-calcareous rock, such as Gneiss.
Analysis shows, that the species numbers in the western parts of the country are on average lower than in the eastern parts. The geographical regions with the highest florisitc diversity are the Valais, the Ticino, the Grisons and the eastern part of the Northern Alps. 
A link was found between the species number per mapping unit known from herbarium specimes only and the nearest herbarium. The species number per mapping unit known from the literature strongly depends on the quality of the Flora available.