CONTENTS 



Page. 



Introduction 7 



Kinds of rusts in the United States 8 



Distribution of rusts in the United States 8 



General statement 8 



Areas most liable to rust ^ 



Distribution of the different rust species 9 



Stem rust of wheat 9 



Leaf rust of wheat 10 



Stem and leaf (or crown) rusts of oats 10 



Stem rust of barley H 



Leaf rust of barley H 



Stem rust of rye -' H 



Leaf rust of rye - 12 



Botanical characteristics, life histories, and physiological specializations of rusts. 12 



General statement 12 



Relationships between American and Euroi)ean forms 13 



Stem rust of wheat, rye, oats, and barley 13 



Leaf rust of wheat l-^ 



Leaf (or crown) rust of oats 13 



Leaf rust of rye ^^ 



Leaf rust of barley ^^ 



Biologic forms 1^ 



General discussion I'* 



Experiments on biologic forms 1" 



Description of methods 1" 



Experiments with biologic forms of stem rust 17 



Experiments with biologic forms of leaf rust 23 



Effect of change of host on the mor])hology of the uredospore. . .. . 25 

 General summary of conclusions derived from experiments on bio- 



27 

 logic forms 



The secidial stage of rusts 



History of barberries in relation to rust 28 



Functions of the aecidium 



oo 

 General discussion • • • ■ 



Experiments to determine the vitality of successive uredo generations 



of various grain rusts 



Material used and methods employed 33 



Summaries of the experiments 



Wintering of the uredo generation 



History of the investigations 



Germany 



Denmark 



o , 46 



Sweden 



England 



Australia 



47 

 United States 



Recent experiments on the wintering of the uredospore 



5 



216 



