Some Aspects of the Phytogeography of Tropical Africa

The area covered follows political boundaries and amounts to just over 20,000,000 km', The flora is estimated at about 30,000 species and 2,497 genera.The phytogeographical affinities of the families and genera are analyzed and discussed, as is the comparative poverty of the flora.The main phytogeographical regions and domains are briefly described.The i i flora are analyzed and discussed and some comparison is made with the savanna.The distribution of Indigofera species is analyzed and conclusions drawn.An attempt is made to discuss and assess the endemism at specific and a densities of endemism.Africa has many features in its plant life and elsewhere that combine to make the continent outstanding if not unique among other tropical landmasses.However, these features are not at first sight obvious: the general shape of Africa is undistinguished if not rather dull; so is its topography-there are no great mountain masses to compare with the Andes or Himalayas, and its highest peak, Kilimanjaro, is an isolated voleanic cone that would be no more than "a considerable protuberance" in those great ranges; the flora is not especially rich, and indeed often more noteworthy for its poverty.Yet its fascination is perennial, and not without cause did Richards (1973) entitle a paper "Africa, the 'Odd Man Out'."Poverty and change are perhaps too often the keynotes.Almost everywhere evidence of change is only too obvious: relics of forest disappearing in a sea of grass; senile trees without offspring on the edge of semidesert; lean and hungry livestock pursuing the retreating remains of grazing.Sometimes the pace is slower; only occasionally is ecological change for the better.The remarkable pictorial record of Shantz & Turner (1958) is often revealing.The flora itself and its distribution constantly show evidence of gigantic and destructive climatic changes in the past-evidence in the form of floristic poverty, spectacular