PREFACE 



Students of Plant Disease are naturally divided into 

 two categories. First : those who wish to recognize and 

 treat diseases, without the burden of long study as to their 

 causes ; second : those who desire to study the etiology of 

 diseases, and to become familiar with the parasites which 

 are often their cause. 



The present book is designed to meet the needs of the 

 first of these two classes of readers. It indicates the chief 

 prominent characters of the most destructive plant diseases 

 of the United States, caused by bacteria or fungi, in such 

 a way that in most cases reliable diagnoses may be made, 

 though it must be recognized that in some cases certainty 

 cannot be had without recourse to microscopic details. In- 

 formation is given regarding the best methods of prevention 

 or cure for these diseases. 



In this volume only such characters are used as appear 

 to the naked eye or through the aid of a hand lens, and all 

 technical discussion is avoided in so far as is possible. No 

 consideration is given to the causal organism except as it 

 is conspicuous enough to be of service in diagnosis, or 

 exhibits peculiarities, knowledge of which may be of use in 

 prophylaxis. 



While, in the main, nonparasitic diseases are not dis- 

 cussed, a few of the most conspicuous of this class are 



