fides of the author, but good hand-drawings are always better for reference, 

 if they can be relied on." Notwithstanding this criticism, the present work 

 proceeds largely on the same lines, for the unquestioned fidelity to nature 

 which photomicrographs represent, far outweighs the seeming clearness 

 and explicitness of an ordinary drawing. It is really astonishing to find 

 how often scientific error is perpetuated, because it is based on drawings of 

 what the author imagined but did not really see. 



I have to acknowledge the valuable aid given by my former Assistant, 

 Mr. G. H. Rotinson, and my present Assistant, Mr. C. C. Brittlebank, as the 

 various photomicrographs executed by them show strikingly the essential 

 features of the different species. 



To all who have generously supplied specimens and copies of their papers 

 relating to the subject, I tender my sincere thanks. I am specially indebted 

 to Professor Ewart, Government Botanist, who allowed me free access to 

 the National Herbarium, and to the Director of the Royal Gardens, Kew, 

 who readily placed at my disposal such specimens as were available only 

 at that institution. My colleague, Mr. C. French, Government Entomologist, 

 and his Assistant, Mr. C. French, junior, have been indefatigable in securing 

 specimens, and noting the distribution of these harmful parasites. 



It is hoped that the work may prove useful in the education of the farmer, 

 who is now becoming alive to the necessity of knowing the nature of the 

 pests which devastate his crops, for it is mainly by the knowledge of the habits 

 of the parasites which cause the disease that disease prevention can be 

 secured. 



Not only to the man on the land does this work appeal, but now that 

 Agricultural High Schools and Colleges are established in most of the States 

 and a Chair of Agriculture has been founded in Sydney University, the 

 diseases of plants should become a recognised subject of study at all such 

 institutions. It is beginning to dawn on the minds of our legislators that the 

 importation of pests must be stopped, so that a Quarantine Act has been passed, 

 and it is only a step further to realize that the spread of disease within the 

 States must also be checked. All this legislation will demand increased 

 knowledge on the part of those who have to administer such Acts. 



Attention is frequently called to the small average yield of wheat produced 

 by the Commonwealth — lOJ bushels to the acre — and how to raise it is 

 often discussed. While careful cultivation, suitable rotation, and judicious 

 manuring will all tend in that direction, it is hardly ever thought worthy 

 of mention that the ravages from various preventable diseases are responsible 

 for a considerable amount of the annual shortage. 



With irrigation and intense culture, it is soon discovered that the sunshine 

 and the water, which promote the growth of our cultivated plants, favour 

 their parasites as well, and thus the study of Vegetable Pathology is becoming 

 more and more a matter of national importance, and must soon cease to be, 

 as it is at present, a neglected department of knowledge, if the industrious 

 settler is to reap the full reward of his labours. 



Melbourne, April, 1910. 



