80 EXPLOITATION OF PLANTS 
so far carried on in the tropics, land, crops, transport, 
capital and labour, and only when all these factors come 
into proper operation is there any real exploitation 
going on. When no exploitation occurs, it is the duty 
of the rulers to study the question, and find out which 
factors are not in proper operation, and to bring them 
into bearing, as I have endeavoured to indicate in 
sketching the conditions of the problem in the great 
valley of the Amazon. 
But now, in conclusion, this is a scientific course of 
lectures, indicating in general the applications of botany 
to agriculture, and one will naturally ask, after hearing 
that the conditions which govern tropical exploitation 
or its absence are mainly political or economic, where 
does science, and especially botany, come in? Well, 
except in one or two directions, it does not come in 
until all these preliminary conditions for successful 
agriculture have been fulfilled. 
Botany has’ obviously nothing to do with transport, 
finance, labour, or land, and it is only in the section 
crops that it enters into the problem, but it enters there 
.in a very important way. The earliest agriculture in 
the tropics, as has been mentioned, was concerned 
naturally with those plants of the indigenous flora which 
experience had shown to be useful, but very early in 
the history of the opening up of the tropics by the white 
man it was realised that there might be crops which 
would be more profitable to cultivate than these. The 
Portuguese in the sixteenth century already set about 
introducing into the various parts of their empire the 
crops of other portions, and at the present time most 
of the crops that grow in Ceylon in the gardens and 
