488 WEST AFRICAN FORESTS AND FORESTRY 



evaporation ; whereas the greater part of it might have been stored 

 up in the forest to form perennial, almost unaltering springs, streams 

 and rivers. Two interesting examples of this are seen in the slight, 

 almost negligible rise in the Okwo and the Igbagon streams of the 

 Benin province. Both of these rivers rise in thick forest, and thick 

 forest is also found on their banks. 



In a similar way, instead of the water of the rivers being used for 

 irrigating land which is sandy and dry in the dry season, it rushes 

 away into the ocean for nothing. The flooding of much of the land 

 near the rivers also kills many large forest trees and causes a rank 

 growth of shrubs, creepers and grass, which form the breeding-places 

 for tsetse and other harmful flies. It is rare to find any infected tsetse 

 flies near a clear perennial stream in the forest. 



4. The forest improves the soil of a locality, whether in the 

 primeval or the planted forest. The trees stand at least eighty years, and 

 sometimes for several hundred, on the same land, before being cut down. 

 During this period the tree roots with their root-hairs are penetrating 

 far and wide into the soil, subsoil, and even underlying rock, gradually 

 causing the two latter to weather into finer and better constituent 

 parts. For instance, nothing appears so solid as a mountain of 

 granite ; nevertheless, at the base and to the lee-side of each boulder, 

 more especially if there is any tree-growth there, a beautiful little 

 bed or pocket of blackish soil will be found. Then, again, besides this 

 weathering of the subsoil and rock, the tree leaves, even from ever- 

 green trees, fall down, gradually decay, and form a thick layer of humus. 

 This in itself forms an almost ideal seed-bed. At the edge of forests 

 this humus is washed out on to the agricultural lands and thus enriches 

 them ; furthermore, drj' leaves are blown out of the edge of the forest 

 on to neighbouring agrcultural land, become dug in, or drawn into 

 the land by insects, and so tend to enrich it. In many civilized 

 countries a regular business is done in taking litter and leaf-mould 

 out of the forest to neighbouring garden and farm lands. 



It is a well-known fact that when a forest is cut down after some 

 hundreds of years many plants appear in the clearing which did not 

 exist in the forest before, or, in fact, were not known in that locality, 

 the seeds having lain dormant during the whole period of time. This 

 clearly shows that the forest soil is an ideal medium for preserving 

 seeds, and that it improves rather than deteriorates, which is the 

 case with bare land. An instance of this from the Tropics is seen 

 in the way in which the Corkwood or Umbrella Tree {Musanga Smithii) 

 comes up after the mahogany and evergreen forest has been cleared. 

 No Musanga trees are usually found in the primeval forest. A parallel 

 example from Europe is seen in the way in which Atropa belladonna 

 almost invariably appears when a beech forest is cut down. 



Planting trees and thus forming a forest, though expensive, is 



