FORESTRY 203 



of shed needles below them prevents all but the heaviest and most 

 continuous rain from penetrating to the deep subsoil. Eucalyptus, 

 on the contrary, is said to be highly efficient in both these re- 

 spects. The question of the intervention of different trees between 

 rainfall and drainage probably depends upon a variety of morpho- 

 logical, physiological, and ecological characters which could be 

 revealed by research. 



The influence of tree species on soil type is also of great import- 

 ance. It is well known that in Europe conifers are associated with 

 podsolic soils, and broad-leaved trees with brown earth and kin- 

 dred soil. That is to say, in a climate and on a soil on which either 

 grow, it appears that conifers bring about soil deterioration, 

 whereas broad-leaved species, maintaining a high base-status in 

 the surface soil, bring about soil improvement, or at least maintain 

 the status quo. The recent concentration on the planting of conifers 

 in Great Britain has been criticized on this account, on grounds 

 which may be found applicable also in Africa. These questions 

 are fundamental to the formulation of forest policy and deserve 

 careful enquiry. 



TIMBERS 



The early descriptive work on African timbers suffered from the 

 fact that the correct identity of the species of which the woods were 

 described was not always established, hence much of it is unreliable. 

 Systematic descriptions of the anatomical structure of African 

 woods have been in progress at the Imperial Forestry Institute for 

 some years, special care being taken to establish, with the help of 

 botanical specimens, the correct identity of each species dealt with. 



Several hundred authentically-named wood specimens have 

 been received by the institute and a new series of publications 

 entitled Forest Trees and Timbers of the British Empire, brought out 

 by the institute (1932-5), contains information on the taxonomy 

 and habits of forest trees and anatomical descriptions of their 

 woods. Three of these are now available, dealing respectively 

 with some East African Coniferae and Leguminosae, twenty West 

 African timber trees, and fifteen South African high forest tim- 

 ber trees. A fourth on fifteen Uganda timber trees will appear 



