86 Report of the Botanist of the 



The treatment fails for the following reasons : ( i ) The removal 

 of so many leaves checks the growth of the plants. In a supple- 

 mentary experiment made in 1900 the removal of 10 leaves (one or 

 two each week) from each plant reduced the yield by 42.8 per ct., 

 or at the rate of three tons per acre (page 106) ; (2) Infection occurs 

 through the roots as well as by the way of the leaves; (3) Infection 

 may occur at the base of the leaf close to the stem and get into the 

 stem unobserved ; (4) The germs of the disease are so widely and 

 so abundantly distributed that it is useless to try to stamp out the 

 disease by the removal of diseased material. 



No successful method of combating the disease is known. Further 

 experiments on treatment are in progress ; also, investigations on 

 the mode of infection and dissemination, as it is believed that these 

 fundamental problems must be solved before much progress can be 

 made toward the control of the disease. 



