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purpose of cultivation may carry the germs of the disease from 
infected to healthy trees, or from diseased to healthy groves. 
Besides, the gum may act as a preservative for the conidia, and 
thus prolong their vital activity. During irrigation, gum with 
conidia might easily be carried from diseased to healthy trees, 
more especially when the water is allowed to flood up to the 
trees. It is not maintained that this is the only way in which the 
disease is spread, but it is sufficiently evident to be worthy of 
being guarded against. 
Varieties affected. —J am not aware that any particular varieties 
have been specially noted in Australia as being affected with this 
disease, further than that it has been observed on oranges and 
lemons. But in Florida the susceptibility of different kinds has 
been carefully observed. The most susceptible appears to be 
sweet seedling orange trees ( Citrus aurantium) f ixu& stocks of this 
used for budding are also liable. Then the lemon ( Citrus 
limomim ) in all its varieties is very commonly affected, but the 
Shaddock ( Citrus deamana) is less liable to the disease than 
either of the two preceding. Mandarin oranges ( Citrus nobilis) 
are only occasionally affected, and the Seville or bitter orange 
(Citrus bigaradia ) is the least susceptible of any, being almost 
entirely free from it. This points to the use of the sour orange 
as a stock for budding, and Swingle and Webber write :—“The 
sour (Seville or hitter) orange, used as a stock for budding, 
remains free from attacks, and in Florida its use for this purpose 
is almost a sure preventive of the disease/’ The liability or 
non-liability to disease is a matter requiring to be tested in 
different localities with their varying conditions of soil and 
climate, so that the order of resistance in Florida does not 
necessarily imply a similar resistance in Australia. It is to be 
hoped that experimental tests will settle the best and most 
suitable varieties to be used in different districts of Australia. 
History of disease in Australia. —In the evidence given by 
C. Moore, F.L.S., late director of the Botanic Gardens, Sydney, 
before the Victorian Royal Commission on Vegetable Products, 
lie stated that this disease was very destructive to the oranges 
about Sydney as far back as 1867. Then the late Mr. Neilson, 
curator of the Iloyal Horticultural Gardens, Burnley, gave evi¬ 
dence that he had experience in the gardens of what is known as 
the Sydney disease, and recommended the following means of 
dealing with it :—“ I have come to the conclusion, as far as I am 
concerned, personally, that in a great measure it is attributable 
lo deep planting. In planting the orange now, I keep the tap 
roots upon the surface, and all that I have used in that method I 
have never found the slightest symptoms of decay. Another 
causo I think is in watering—in putting the cold water upon a 
very hot day close to the bark of the tree, that causes sudden 
evaporation, which chills the bark; that is the reason that I 
