viii DISEASES OF CULTIVATED PLANTS 



endeavour, by means of spraying alone, to keep it under sub- 

 jection. Diseased branches, fruit, etc., should be removed 

 in fact, as far as practicable, all diseased material should be 

 destroyed. Unfortunately it is not always possible to do so, 

 as when potatoes attacked by Black scab, or turnips suffering 

 from Finger-and-toe rot in the ground. In such cases the 

 land should be sterilised by the use of quicklime or gas-lime. 



Much has been written of late respecting the great advan- 

 tage derived from certain fungi parasitic on insects. Such 

 statements are perfectly true ; myriads of destructive insects 

 are destroyed by such means. This has happened in the 

 past, and will continue in the future. The one thing to 

 refrain from is that of investing money in any scheme having 

 for its object the extermination of injurious insects through 

 the agency of fungi. Any such investment will be regretted. 



The numerous references given in this book indicate my 

 great indebtedness to other investigators, to whom I respec- 

 tively tender my best thanks. Finally, to my colleague, 

 Mr. A. D. Cotton, I am indebted for calling attention to 

 many subjects which would otherwise have been omitted. 



GEO. MASSES. 



GATEACRE, KEW GARDENS, 

 January 28, 1910. 



