The historical (mainly from the 1930s) and current records of 482 vascular plant species or genera of non-littoral areas of 464 islands in the archipelago of SW Finland are compared to visualise changes in distribution patterns and to identify environmental variables that affect the distribution of the species. The environmental variables were measured in the GIS. Logistic regression analysis was used to find variables that affect the probability of species occurrences. Results, including distribution maps, are presented for each species. A synthesis of the study is presented in the last part of this article series.