It is a noteworthy fact that there has been available to student and reader no general text or reference book of American origin upon fungous diseases of plants. Nevertheless, for thirty years or more there has been active investigation in this field, and during much of this time instruction in plant pathology has been an important part of biological teaching in all colleges where plant industry or country-life interests have been adequately represented. In the agricultural colleges the teaching of general mycology has been important, and that of plant pathology is now essential. The presentation should be fundamental, but it should also bear a close relation to the affairs of life. Plant pathological work has been rapidly developed in all countries characterized by a progressive agriculture, and for European conditions the student experiences no great lack of reference works.

Through the agricultural experiment stations and through the extension work in various states a vast amount of information with respect to plant diseases has been published and otherwise disseminated, so that to every intelligent plant producer the opportunity has been extended of becoming more familiar with the crop relations of destructive parasitic fungi. The student and the progressive grower require something further, and it has therefore seemed none too early to put in book form a comprehensive discussion of the chief fungous diseases of cultivated and familiar plants. It is not intended that this book shall be an introduction to systematic mycology; yet the arrangement of the material in taxonomic sequence with respect to the fungi largely eliminates the necessity of any mycological preparation as a prerequisite.

As far as practicable, in the discussion of each disease, three important considerations have been kept in view: (i) to describe the pathological effects and other relations of host and parasite; (2) to make clear the life history of the causal fungus; and (3) to indicate the approved or suggested methods of prevention or control. The author fully recognizes that in any complete discussion of a fungus disease there are definite theoretical subdivisions, such as symptoms, pathological morphology, etiology, life cycle of the causal organism, etc. Nevertheless, such a system does not at present recommend itself. In the nomenclature of popular names of diseases uniformity, or special fitness, at a sacrifice of established usage, has been avoided. An extensive host index has been included in order to present in a succinct form all of the diseases discussed upon any host. It is, perhaps, needless to add that the chapters upon culture methods, technique, and physiological relations are designed primarily for reference, and to stimulate the most complete use of the available material. The bibliography is intended to be suggestive, and the titles are made prominent that the suggestion may not be avoided.

Aside from photographs and drawings made by the author, the illustrations have been derived from a variety of sources. Special acknowledgment is made to Mr. F. C. Stewart, of the New York Agricultural Experiment Station, and to Professors H. H. Whetzel and George F. Atkinson, of Cornell University, for the privilege of using many negatives from their collections. Many others have kindly furnished material for one or more illustrations, as credited in the legends. In the preparation of the drawings much assistance has been given by Mrs. B. M. Duggar. For helpful suggestions respecting the manuscript and for a first draft of the synopsis of species among the Uredinales, the writer is indebted to Professor George M. Reed, of the University of Missouri.