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 9 



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 11 



Leaf rust of barley 11 



Stem rust of rye 11 



Leaf rust of rye 12 



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



General statement 12 



Relationships between American and European forms 13 



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



Leaf rust of wheat 13 



Leaf (or crown) rust of oats 13 



Leaf rust of rye 14 



Leaf rust of barley 14 



Biologic forms 14 



General discussion 14 



Experiments on biologic forms 16 



Description of methods 16 



Experiments with biologic forms of stem rust 17 



Experiments with biologic forms of leaf rust 23 



Effect of change of host on the morphology of the uredospore 25 



General summary of conclusions derived from experiments on bio- 

 logic forms 27 



The aecidial stage of rusts 28 



History of barberries in relation to rust 28 



Functions of the secidium 32 



General discussion 32 



Experiments to determine the vitality of successive uredo generations 



of various grain rusts 33 



Material used and methods employed 33 



Summaries of the experiments 34 



Wintering of the uredo generation 45 



History of the investigations 45 



Germany 45 



Denmark 46 



Sweden 46 



England 46 



Australia 47 



United States 47 



Recent experiments on the wintering of the uredospore 49 



216 5 



