AUTHOR'S PREFACE. 



In my research work, and in connection with my lectures at 

 the University and Technical School of Munich, I have for 

 some time felt convinced that there existed a very evident gap 

 in the literature relating to the diseases of plants. There was 

 need of a newer and more complete work on cryptogamic para- 

 sites and the diseases induced by them on higher plants, a work 

 furnished with many accurate illustrations, with a survey of 

 the newer literature, and with a general part wherein parasitism 

 and the relations between parasite and host are discussed from 

 a botanical standpoint. Therefore, I have undertaken to write 

 a book intended to supply in some degree this pressing want. 

 Here the attempt has been made for the first time to review 

 in a general and comparative manner the biological, physiological, 

 and anatomical relationships accompanying the phenomena of 

 parasitism. Already De Bary has considered the varying degrees 

 of parasitism and the phenomena of symbiosis in his celebrated 

 Morplwlogy and Biology of the Fungi ; while Wakker has laid 

 the foundations of our knowledge of the alterations in the 

 anatomy of plants diseased by the agency of fungi, more especially, 

 however, those alterations accompanying 'hypertrophy.' I venture 

 to continue this difficult and comprehensive chapter of plant 

 physiology, because for ten years I have devoted my time to 

 the study of plant pathology. The book may be all the more 

 acceptable since I have confirmed a large number of the 

 observations and added the results of my own investigations, 

 many of them now published for the first time. 



The present time is favourable to my work. The great 

 Sylloge Fungm-um of Saccardo (with its appendices in Vols. ix. 

 and X.) has been recently completed ; the classic investigations 



