x Preface. 



the spraying of plants and the fundamental principles under- 

 lying this operation. 



As to the future, it can only be said that the prospect for 

 broadening the work so well begun is exceedingly promising. 

 As yet it cannot be stated that we have a well-defined science 

 of plant pathology, but gradually the investigations and thought 

 in this direction are being crystallized. Tt is now realized that 

 to truly understand and appreciate pathological phenomena we 

 must be familiar with physiology, the normal life processes of 

 plants. After all, the highest aim of the investigator in this 

 field of research is not to deal only with effects as he finds 

 them, but to study causes, as it is only by this means that 

 the true nature of many of the phenomena involved can be 

 obtained. Following this line, we shall in the future look for 

 a science capable of elucidating the problems which form the 

 very basis of agricultural and horticultural pursuits. 



B. T. GALLOWAY. 

 WASHINGTON, D.C. 



