9 
of treatment, but such as are given are based upon what we 
know of the most successful measures employed against 
similar fungi oil closely allied plants, mainly however from 
the results obtained in Florida by officers of the Division of * 
Vegetable Pathology of the United States Department of 
Agriculture. With the thoroughness and knowledge char¬ 
acteristic of that department two officers were deputed to 
study these diseases on the spot, and a laboratory was 
specially erected for the purpose. The results are given in 
Bulletin No. 8, entitled u The Principal Diseases of Citrus 
Fruits in Florida ” by Walter T. Swingle and Herbert J. 
Webber, and Bulletin No. 13, 44 Sooty Mould of the Orange 
and its Treatment.” by H. J. Webber. I have also given 
attention to the fungi which aid the grower in destroying 
those pests which injure his crops, for by pitting nature 
against herself he is using a powerful ally. 
In the second part the minor diseases are dealt with, and 
technical descriptions are given of the various fungi found 
upon citrus trees in Australia. This is the most difficult 
part of the task, involving laborious research and micro¬ 
scopic investigation of fungi which are often unknown to 
science, and yet it is genera lly the least appreciated. In the 
case of insects they are usually of an appreciable size, and 
appeal to the ordinary observer, but the fungi are often 
hidden in the tissues of the plant, and only reveal their 
presence by the mischief they do. Hence all sorts of reasons 
are assigned as the cause of these mysterious diseases as they 
are called by people who do not take the trouble to investi¬ 
gate, and who perhaps never handled a microscope in their 
lives. Of course it is much easier to talk learnedly about 
sun scald, or frost bite, or chilling at the roots, or speak of 
die back, black disease, and so on, rather than to probe the 
matter to the bottom and prove the cause they assign to be 
the correct one. In speaking of the effects of the researches 
of De Bary, Tulasne, and others, Professor li. Hartig, of 
the University of Munich remarks in his “Text Book of the 
Diseases of Trees ”—“The view hitherto held that all fungoid 
growths appear only as the result of previously existing pro¬ 
cesses of disease, or as indications of the incipient death of 
the part of the plant which is attacked was shown to be 
erroneous.” It was then recognised that the tracing of 
causes is absolutely necessary before remedial measures can 
be rationally applied, and wherever fungi are concerned they 
require to be fully studied with all the conditions favouring 
