The aim of the project is to cover all vascular plants known to occur in Somalia, and establish a foundation for all future plant related work in the country. This volume is the last to appaer in a series of four and covers 33 families with a total of more than 1000 species, of which 137 have been described as new within the project. Twenty eight further new species, described in the last few years, which are additional to the previuos published volumes 1, 2 and 4, are included in the appendix, along with a number of species that represent new records for the country. Indexes vernacular and scientific names conclude the volume, and a cummulative index to all four volumes is also provided.