vi author's preface. 



of Brefeld in the domain of mycology, and containing his 

 classification of the fungi, are now well advanced ; the Erypto- 

 ganun-Flora of Eabenhorst is nearly completed ; and the newer 

 literature and observations are now periodically reviewed in the 

 Zeitschrift fiir PJlanzenkrankheiten, and other magazines. The 

 recent publication of several investigations on the infl^uence of 

 parasites on the anatomy of their host-plants greatly facilitated 

 the compilation of the general part of the work. 



I have here attempted to summarize in a systematic manner 

 the preventive and combative agencies available against the 

 more important diseases of economic plants. In many cases 

 these are supported by facts given in the chapters on the 

 natural and artificial infection of host-plants, and their disposition 

 towards diseases produced by lower organisms. 



As already indicated in the title-page, the book deals only 

 with those diseases of plants produced by the cryptogams and 

 other lower organisms of the vegetable kingdom. The large 

 number of parasites which attack such lower plants as algae 

 and lichens, although not altogether neglected, have as a rule 

 been omitted, otherwise the book could not have been brought 

 within the limits of a single volume. In the second or systematic 

 part of the book, the pathological phenomena are considered 

 along with the description of the organism producing them. 

 Where the diseases are of economic importance, measures for pre- 

 vention and extermination are also suggested. Notices of greater 

 length are given to such parasites and diseases as have formed 

 the subject of special investigations. We could only aim at a 

 complete list for Germany and the neighbouring countries, yet 

 we have included many species of interest occurring in other 

 parts of the world, notably in America. 



Though it will be possible to identify most of the more 

 important parasites by the aid of this book, we do not intend 

 it to replace the systematic works ; we purpose rather to add 

 to the descriptions given in Eabenhorst, Saccardo, and similar 

 works. This book is intended above all to be, in the terms 

 of its title-page, " an Introduction " ; hence it seeks to orient 

 in a general way, to give a summary of our knowledge, and to 

 indicate the way to more detailed records. On this account 

 great care has been taken in the citation of home and foreign 

 literature, not only up to the time of finishing the manuscript 



