The first part is devoted to a general account of the principal 
fungus diseases affecting Citrus trees in Australia, and will receive 
most attention at the hands of the practical grower, while this 
second part gives technical descriptions of all the fungi hitherto 
found upon them here, and will be welcomed by those who take 
an intelligent interest in the nature of the causes producing 
certain effects, as well as in the effects themselves. 
It is necessary for inspectors and others who wish to be abreast 
of present day knowledge with regard to fungi in their relation 
to plants to know the various forms which may be met with, so 
as to discriminate between the really serious pests and those 
which are comparatively harmless or positively innocuous. 
One of our most successful Citrus cultivators has recommended 
every grower to be provided with a magnifying glass to examine 
the trees and see the effect of any treatment applied to them, and 
it may he remarked that, for the proper study of fungus diseases, 
the microscope is indispensable. The Government, however, pro¬ 
vides experts to do this work—to diagnose disease and prescribe 
the necessary treatment—but no one can tell exactly the cause in 
many cases without having recourse to microscopical examination. 
Professor Viala, of Montpellier Viticultural College, points out 
that, diseases due to very different causes are often confounded as 
having the same origin. Opinions may have been formed upon 
the external characters of the injury, or upon simple facts of 
observation, while in specifying a disease external characters are 
only of secondary importance. It is doubtless useful to know 
these, but it is necessary first of all to define the alterations by 
their real cause, by the study of the parasite if the disease is of 
a parasitic nature. And even tlie undoubted presence of a para¬ 
site upon the affected part is not sufficient in itself to prove that 
the injury is caused by it. Experiment ought to confirm the 
facts of observation. 
In the following pages the fungi are grouped according to their 
occurrence on fruit or leaf, ou stem or root; hut this arrangement 
has its drawbacks. Several of the fungi are found upon different 
parts of the tree, and the plan strictly followed out would involve 
needless repetition, hut this is avoided by noting any such general 
appearance in connexion with the first mention of the fungus. 
In bringing together the various fungi occurring on Citrus 
trees, their largo number must strike even the casual reader, and 
of these a large proportion are not known in European countries 
considered to ho the present home of Citrus fruits. But it must 
he remembered that for many years the Native Lemon lias been 
almost universally employed as a stock in Queensland and New 
South Wales, and thence imported into Victoria, so that native 
diseases were probably introduced with it. It would he an 
