The useful trees of northern Nigeria

by Hugh Vandervaes Lely

The text is supplemented by drawings of the flower, leaf, thorn, fruit and seed, sketched from the living specimens. Wherever possible the drawings are actual size to avoid calculations from enlarged or reduced figures, but a number have been enlarged to show structures, or reduced owing to their actual size. In several cases sections of various parts have been made to illustrate peculiarities of structure, a pocket lens being used for this purpose, though practically all the parts drawn are visible to the unaided eye.

The majority of the botanical names have been verified through the Herbarium of the Royal Botanic Gardens at Kew.

In describing the woods, few of which are in use and many of which are little likely to be of use, an attempt has been made to strike a path midway between the complete technical and botanical description employed with regard to timbers and a vague statement as to colour, quality, hardness and grain which helps little to distinguish the individual from others like it. Most of the woods are described from samples collected by the author and shaped by the Sokoto Arts and Crafts School. I am indebted for these, and for the facilities offered for observing their behaviour under tools, to Mr. W.E. Nicholson. The dry weight of seasoned wood is given in all cases and in this connection it may be noted that a number of species produce heavier wood in the north than they do in the south.

A table of flowering seasons has been appended, with a few notes on its significance.

A second appendix arranges the 120 species under their Families. The Genera Plantarum of Bentham and Hooker has been followed.

Finally, there is an index of Hausa names for reference to the plates and text, whose numbers are given in the index. A blank column has been left in the index for the benefit of those who may desire to collect either additional Hausa names or the nomenclature of other tribes. It is hoped that the scope of the volume will be enlarged thereby, so as to cover other parts of Nigeria where the trees are the same but the language different.

The botanical name, being universal, is always given preference. The native names, variable and unreliable as they often are, should be a secondary consideration, their importance resting in their being a means of communication with the native rather than a short cut to the botanical names. In a country where there are several native names for one tree or one native name for several distinct species, the knowledge gained is either limited to a small number of trees or applicable to a small area of country. But once examined and properly identified, no number of native names need confuse the real identity. In collecting native names a warning should be given against the ignorant or ready-to-please native, and independent corroboration is advisable before accepting a name as worth recording. At the same time it is a fact that names genuinely differ in quite small areas of country where the same language is spoken, and a knowledge of the botanical names or real familiarity with the tree species is essential to reliable work.

The identification of 120 species, though seemingly not a large number, is sufficient to afford a thorough familiarity with most of the savannah forests and makes further species, not included here, stand out all the more clearly from their no longer similar companions. Numbers or economic values of further species are sufficient justification for forwarding these for identification to Kew, if they cannot be named from their resemblance to known species or by means of a Flora.

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.