In selecting the 120 species to be included in this volume, the author has had to exercise his own discretion. The collection has been made between 9° and 14° N., and those who know this area will find a great deal they require, while some, in the more northerly latitudes, will find little of importance that is not included. Others, however, will meet with unfortunate omissions, for the following reason: South of 11° N. certain species which more truly belong to the evergreen and intermediate forest zones have established themselves in considerable numbers by streams, in valleys and in pockets of rich soil with surroundings suited to their propagation. Either all or none must be included if this volume is to be representative of such regions, but since they are not truly savannah species their inclusion here is beyond the scope of this volume, which would have to be enlarged very considerably to cover even the forests in the Benue region and south of the Niger, where savannah abounds. All the species included here occur up to 11° N., and with five exceptions up to 12° N., while nearly all occur below 10° N. and many much further south. A selection has been made in the case of some genera, _e.g._, _Ficus_, and _Combretum_, to familiarise the characters of trees which occur in large numbers and are typical of savannah forest. Some of these are of little importance beyond their occurrence in numbers over large stretches of country. The value of trees varies largely according to locality. Timber value is of little account in regions where it is inaccessible and unexploitable. Food, medicinal and other values take precedence where there is a large population demanding economic produce, and many species must be accounted valuable merely as a soil covering for the prevention of denudation, fixation of shifting surfaces, protection of new growth, grazing areas, precipitation of moisture, retention of conditions advantageous to agriculture or as a basis for the introduction of new, or the encouragement of existing valuable trees from the forestry standpoint. The advance of agriculture or the condensing of population intensifies these values by the destruction of the better types in favour of the poorer, and by the increased demand for the products of the better types. There are many instances of valuable products being obtained from forests which are not only some distance from habitations but whose soil is of a nature that precludes any possibility of supporting a population, since it will not produce crops. For example, _Sclerocarya birrea_ (Danya) grows to large sizes in some parts of Sokoto Province where the soil is of an unworkable kind and where, over wide areas, there are no people. Yet this area is visited from all over the country and hundreds of trees are felled for the manufacture of mortars, trees in many cases suitable for two or three mortars being exploited for one only.