Historical (mainly 1930s) and contemporary 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 a GIS. Logistic regression analysis was used to find variables that affect the probability of species occurrences. Results, with distribution maps, are presented for each species. The families Rosaceae, Fabaceae, Onagraceae, Sapindaceae, Oxalidaceae, Geraniaceae, Polygalaceae, Cornaceae, Apiaceae, Rhamnaceae and Rubiaceae are presented in this fourth part of the series. A synthesis of the study will be presented in the last part of this article series.