88 SYLVICULTURE IX THE TROPICS . , 



hopelessly destroyed by fire, whereas a slight scorching 

 of the teak fruit, on the contrary, seems to stimulate 

 termination. 



In the Sudan it is a well-known fact that a fire 

 passing through the open forests of Acacia Verek not 

 only kills a large number of trees, especially those 

 weakened by repeated tapping for gum, but that it also 

 stops the supply of gum for the season. It is a curious 

 fact that in the case of the Acacia, which is next in 

 importance to the above in the production of gum in 

 the Sudan, viz. Acacia Seyal, the same rule does not 

 seem to hold, and that gum production appears to be 

 stimulated by forest fires, although the quality of the 

 gum is reduced by them. 1 In the forests of both of 

 these species, the heavy growth of grass which springs 

 up operates against successful natural regeneration, and 

 experiments made show that the seed germinates and 

 the seedling establishes itself best where there is no 

 grass. It is therefore probable that, unless light 

 ploughing in the sandy soil in which A. Verek thrives 

 can be carried out expeditiously and cheaply on a 

 large scale, it will be necessary to close certain 

 blocks periodically to tapping, and by setting fire to 

 the grass to encourage natural reproduction ; and, 

 when this is accomplished, they can be protected again 

 from fire in order to enable the collection of gum to 

 proceed. 



It is out of the tropical zone, in the coniferous 

 forests of North America, that forest fires cause the 

 most awful devastation ; in the Tropics I know of no 

 forests which have to endure such destruction as that 

 caused sometimes over thousands of square miles by a 

 single forest fire in North America. So much, however, 

 has become apparent that, apart from the consideration 



1 Recenl research (see Fourth Report of tlie Wellcome Tropical Research 

 Laboratories, Khartoum) seems to indicate that the propagation of the gum- 

 bacillus is due to ants. It is possible, therefore, that in the forests of A. Verek, 

 where the trees arc smaller ami more scattered and the soil sandy and more 

 easily heated, there is a greater destruction of ants by fire than in the- denser 

 and taller forests "I' ./. Seyal growing on cotton-soil. 



