8 
Some growers are of opinion that all fungi are more or 
less saprophytic, that they only occur when the plant is 
diseased from some other cause, but even a slight knowledge 
of the nature and mode of life of fungi would soon dispel 
such an idea. Saprophytes, however, may be and often are 
mistaken for disease-producing fungi, and therefore it be¬ 
comes necessary to recognise them as such, in order to 
prevent unnecessary alarm. 
Taking the occurrence of fungi on still living and growing 
parts, as indicating generally their parasitic nature, I have 
provisionally considered 38 species as more or less parasitic, 
and of these only the more important from an economic 
point of view have been treated at length. 
If the diseases of citrus trees be regarded from a general 
stand-point, it is noticeable how large a proportion occur 
upon the orange and lemon. 
In Saccardo’s “ Sylloge Fuugorum ” Vol. XII. Part II., 
Division 1, a Host-index is given containing all fungi with 
the plants on which they occur up to the end of 1897. On 
the orange (Citrus aurantium) there are 83 species, and on 
the lemon (C. limonum) 58 species, six of which are also 
found upon the orange, so that the latter is infested by the 
greater number of species. If we compare the 82 Australian 
species as to their distribution on orange and lemon trees re¬ 
spectively, it is found that 25 belong to the former and 31 to 
the latter along with eighteen common to both. Three occur 
on the citron, two on the shaddock, and three are parasitic 
upon scale insects. Saccardo gives the number of fungi on 
citrus trees, irrespective of their being parasitic or saprophytic, 
so that, a recent notice of this work in an Australian agricul¬ 
tural journal, in which the number of fungi Avere stated as if 
all Avere disease-producers conveyed a false impression. 
It is hoped that the plan followed in this publication may 
enable those interested to recognise the diseases and to treat 
them with success. In the first part only the more promi¬ 
nent and destructive diseases are dealt with, although it has 
to be borne in mind that many of those considered less 
important do a deal of damage in the aggregate, undermining 
the health of the tree, diminishing the yield of fruit, deterio¬ 
rating its quality, and rendering it more liable to decay. The 
description of the disease is given in plain language so that 
the Ordinary grower may recognise it, and the treatment is 
based upon a knoAvledge of the exciting cause. I have not 
had the opportunity of thoroughly testing the best methods 
