RUBBER AND RUBBER PLANTING 177 



Hundreds of thousands of trees of the same species are 

 here arranged in regular rows, their leaves and roots 

 actually intermingling. The conditions are therefore 

 ideal for the development into an epidemic of any 

 disease which may make its appearance. 



Epidemics. 



Consequently the occurrence of epidemics under the 

 conditions described is by no means unknown. One of 

 the most famous examples of modern times is afforded 

 by the coffee leaf fungus Hemileia vastatrix, which, in 

 combination with other diseases, entirely ruined the 

 coffee planting industry of Ceylon in the seventies and 

 early eighties. This calamity has taught planters in 

 general a lesson which it is to be hoped they will not 

 readily forget; for if a disease be taken in hand in its 

 early stages, when only a few individuals are affected, it 

 is generally possible to cope with the trouble to some 

 extent and to prevent its universal spread. With this 

 object in view, superintendents are now instructed to 

 keep a close look-out for the first indications of disease; 

 and expert plant-doctors entomologists and mycolo- 

 gists are maintained in all important tropical planting 

 countries. It is their business to diagnose correctly any 

 symptoms of disease which may appear, and to prescribe 

 the most appropriate remedies which science has been 

 able to devise. 



And, just as in the case of human ailments, the 

 L. 12 



