THE TANGANYIKA PROBLEM. u 7 



Once started, the groups of trees and patches of 

 bush which marked the graves of their former bene- 

 factors, the euphorbias, spread gradually under the pro- 

 tection of their own shadows, until finally the patches 

 ran together and more or less coalesced into the ragged 

 forest which covers the higher portions of these long 

 alluvial slopes. 



It will be obvious that we have thus, in the simple 

 natural dispersion and growth of euphorbias over desert 

 steppes and in their mode of growth, a completely satisfac- 

 tory explanation of the formation of park-lands, and their 

 relation to steppes and forest ; the process of their forma- 

 tion being a natural sequence of events following upon 

 the scattering, through the agency of the wind or birds, 

 of the seeds of a single tree. But at the same time the 

 appearance of a park-land is seen also to be one phase in a 

 series of changes which follow the retreat and drying up, 

 or the change in position, of water on the face of the land. 

 And further, it appears to be as true of the natural park as 

 of the artificial one, that unless it is kept up, it must, in the 

 course of time, disappear and become converted into more 

 or less thick forest. Its appearance is simply the ex- 

 pression of progressive physical change. There appears to 

 be no agency, except a park-keeper which is capable of 

 maintaining a park, any more in Africa than in England ; 

 and perhaps the most singular, or at any rate the most 

 interesting thing, which the foregoing observations teach us, 

 is that the African parks are absolutely impermanent, and 

 are, in reality, direct and incontestable evidence in them- 

 selves of wide-spread physical changes in the lands on 

 which they exist. 



But not only is the existence of a park-land evidence of 

 recent change in any district in which it may occur, it is 



