FORESTRY 201 



value. For the Gabon region of French Equatorial Africa, there 

 is a published account (A. E. F. 1931) of the forests and forest 

 exploration. Professor Stebbing's book (1937) includes a general 

 account of all the forests of West Africa. 



In the Belgian Congo extensive investigations have been carried 

 out, and valuable matter has been published, notably by Delevoy 

 (1928-9 and 1933), de Wildeman (1920 and 1934), Vermoesen 

 (1923), and Lcbrun (1935). Delevoy's ecological studies in the 

 Katanga are especially important for British workers, since the 

 country described is very similar to that of Northern Rhodesia. 



THE INTRODUCTION OF EXOTIC TREES 



In afforestation there are two primary facts to be held constantly 

 in mind : ( i ) a considerable proportion of Africa is, for reasons of 

 soil and climate, suited only to tree-growing, and (2) a number of 

 the indigenous timber trees are of little value when compared with 

 trees which thrive in other continents. Accordingly the desirability 

 of converting useless African bush land into useful forest by plant- 

 ing introduced trees where a sale may be found for them, deserves 

 consideration. In Southern and Northern Rhodesia and parts of 

 East Africa, the experimental introduction of fast-growing exotic 

 trees, particularly conifers and eucalyptus, has been an important 

 part of the work of the forest departments. Much information has 

 been accumulated, a summary of which has recently been written 

 by Professor Troup (1932). 



In South Africa the reasons for usins: exotic trees are different. 

 They are briefly: (i) an economic demand for the soft woods of 

 commerce, particularly to make fruit boxes, coupled with a pau- 

 city of indigenous forests, and (2) the inability of the indigenous 

 high forest trees to thrive away from their native habitats on the 

 type of land which the division of forestry usually has at its disposal 

 for afforestation. 



The introduction of exotics has created its own problems : some 

 trees have proved to be unsuited to the soil and climate of their 

 new environment, others have succumbed to disease caught from 

 indigenous trees, and still others have brought their own diseases 

 which have taken the upper hand in their new environment or 



