Though much has been written about the various types of savannah forests, a short account of them will not be superfluous here. First it may be pointed out that savannah forests vary so much in their composition and distribution that a survey is practically impossible, and if made, would have to be revised annually. Savannah is a particularly aggressive form of forest growth. Given the opportunity, it at once occupies more land and on its own ground the inferior types oust the superior wherever there is an opening. Any extensive area of cultivation, if abandoned and allowed to regenerate its tree growth, lets in secondary forests containing species which are less exacting as to soil and moisture conditions, and the depreciation of these conditions to the farming methods stops the competitive growth of the trees which formerly occupied the area. Where the area cleared is sufficiently small and the period short enough, the conditions are retained, and are able to close up the clearing with little loss by degeneration. The fringing forests, belts of evergreen and deciduous trees on the banks of streams, are continually hard pressed by the broad wedges of open savannah between them. Fires take toll of them every year and cultivation not only pushes them down stream from the source but interrupts and cuts them up into islands exposed to threats of extinction. Savannah is very topographical, and though, within broad limits, it can be divided into two main types, Tree and Bush savannah, the two are so distributed or blended that the differences are often unrecognisable and not able to be recorded in a survey. Tree savannah is recognised as a tall type having a light, closed canopy, with a sprinkling of under-shrubs and a sparse growth of grass. Bush savannah is a more open growth of less height, more spreading and lower branched form, with no canopy, and many stunted shrubs and a dense growth of grasses which are normally burnt out each year. There is every variation of this latter type from _Combretum_ and _Guiera_ scrub of barren soils or stony plateaux to the type which closely approaches that of Tree savannah. The following are some of the recognised sub-types:—