vi FOREWORD 



point here referred to. There are, in Trinidad, cane areas where 

 variations in agricultural practice have resulted in practical 

 immunity from " Froghopper Blight," yet, in one instance at 

 least, the immune area was contiguous with plantations, other- 

 wise similar, in which the pest had assumed serious dimensions. 

 Further illustrations are supphed, in the body of the work, by 

 the class of " debility diseases," where a sound knowledge of 

 agricultural physiology has been able to indicate satisfactory 

 methods of coping with the onset of the pests. 



Of course the matter is not always so easily brought into line 

 with agricultural practice, and the careful reader will observe 

 the judicious attitude maintained by the author in respect of 

 'Otiier diseases in which the factors are not so simple or so suscept- 

 ible of control. But it is safe to say that no one can peruse the 

 work, more especially if he happens to possess a first-hand 

 acquaintance with the problems under discussion, without feeling 

 that in this book at any rate a successful attempt has been 

 made to grapple with the scientific principles of some of the 

 /larger issues that form the background of plant pathology. 

 It is only in this way, i.e. by an intelligent appreciation and 

 application of principles that the ravages caused by the many 

 and various diseases to which cultivated plants, especially in the 

 tropics, are continually liable can ever be satisfactorily controlled. 



J. BRETLAND FARMER. 

 Imperial College of Science and Technology, 

 London. 



