PREFACE 



This volume is intended to introduce to the student the more 

 important cryptogamic parasites affecting economic plants in the 

 United States, with sufficient keys and descriptions to enable 

 their identification. Technical description of each division, order, 

 family, genus and species when important is given unless the 

 essential characters are to be clearly inferred from preceding keys 

 or text. Gross descriptions of the host as diseased, i. e., of the 

 disease itself, have been avoided since such are to be found in 

 "Diseases of Economic Plants." Effort has been made to avoid 

 duplication of matter contained in that volume. Abundant 

 citations to the more important papers are given, sufficient, it is 

 believed, to put the student in touch with the literature of the 

 subject. 



While many parasites not yet known in the United States are 

 briefly mentioned, especially the more important ones or those 

 which are likely to invade America, no attempt has been made to 

 list all of these. Non-parasitic groups closely related to those that 

 are parasitic have been introduced in the keys merely to give a 

 larger perspective to the student. 



Effort has been made to give at least one illustration of each 

 genus that is of importance in the United States. 



The author is indebted for descriptions, keys, etc., to the 

 various standard works. Those which have been drawn upon 

 most largely are Saccardo's Sylloge Fungorum, Die Naturlichen 

 Pflanzenfamilien of Engler & Prantl, Clinton's Ustilaginales of 

 North America, Clement's Genera of Fungi, and Minnesota 

 Mushrooms, Plowright's British Uredineae and Ustilagineae, Ar- 

 thur and Murrill each in North American Flora. 



The author wishes also to express thanks for suggestions and 

 criticism of the manuscript to T. H. Macbride, who read the por- 

 tion on Myxomycetes; J. J. Davis, Phycomycetes; L. R. Jones 



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