PREFACE VU 



the book were to be read from cover to cover. The plan of the 

 book is intended, however, to facilitate the diagnosis of a dis- 

 ease of a certain kind of tree and to group the diseases of this 

 tree in one place where comparisons may be made. Under 

 each of the host-chapters, the diseases are arranged according 

 to the part of the tree affected and will be found in the fol- 

 lowing order : leaf, twig, branch, trunk and root diseases. 

 The reader is advised to make free use of the index, which will 

 facilitate the finding of those discussions unavoidably scattered. 



It is regretted that specific information is not yet available 

 on many common tree diseases. Most of the leaf-spot diseases 

 have not been studied. Likewise, control measures are largely 

 limited to eradication methods, so far as definite recommenda- 

 tions can be made. This apparently will always be the case 

 for the diseases of the woody parts of trees, until means of 

 naturally or artificially immunizing trees are devised. Spray- 

 ing and dusting for leaf diseases will be practicable when these 

 diseases are better understood. Such methods are expensive, 

 however, and their use will be limited for this reason. 



The author is indebted to Dr. F. D. Kern, who has read 

 the discussions of the rust diseases and offered many helpful 

 suggestions. Grateful acknowledgment is also made to Mrs. W. 

 H. Rankin and to the following co-workers in the Department 

 of Plant Pathology at Cornell University for many suggestions 

 regarding the manuscript and for photographs loaned : Prof. H. 

 H. Whetzel, Dr. L. R. Hesler, Dr. Donald Reddick, Dr. V. B. 

 Stewart, Dr. C. T. Gregory, Dr. H. M. Fitzpatrick, and 

 Miss Edwina Smiley. 



W. Howard Rankin. 



CoBNELL University, Ithaca, New York, 

 September 1, 1918. 



