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The way in which the disease begins in spots or patches, which 
slowly enlarge, the gradual manner in which it spreads from 
country to country and from grove to grove, the fact that trans¬ 
planting affected trees from crowded situations to more open 
localities has brought about recovery, and the appearance of the 
same fungus associated with it in such widely remote countries as 
Italy and Australia, all point to the conclusion that this fungus 
parasite is the immediate cause of the disease. Of course, too 
much moisture around the roots would favour the growth of the 
fungus, and so trees with “wet feet ” would be specially liable 
to the disease ; but it is highly improbable that such a contagious 
disease, and one which has been checked by the application of 
fungicides, should be due to some physiological derangement or 
merely mechanical causes. Dr. Cobb, in bis useful Letters on 
Diseases of JHants f refers to a fungus which he found upon the 
diseased bark of a young Orange stock, and which he considered 
to be a case of apparent “ Collar rot.” ; but there was no evidence 
of gumming, a constant accompaniment of the disease. The 
fungus is not fully described or named, and drawings only aro 
given ; but it is evidently a species of Phoma. If an undoubted 
case of the disease is chosen, the “ Collar rot ” fungus (Lusarium 
limonis ) will be found there. The specimen from which tho 
fungus drawings were made was obtained at Doncaster on 28th 
August, 1896, and the coloured plate represents the stem of a 
Lemon tree obtained at Malvern. The effects of the “rot” were 
visible for at least 6 inches from the ground, and they extended 
to some of the roots, which were quite dead ; but there was 
nothing to indicate tlmt the disease had started at the roots (as is 
the opinion of some) and then spread to the stem. The disease 
had apparently started just beneath the surface, and spread 
upwards along the stem and downwards along some of the roots. 
There is a totally distinct disease,known as “Hoot rot,” which 
is often confounded with “Collar rot,” commencing at or near the 
extremities of the roots and proceeding upwards until the tree is 
killed. The malady is duo to quite a different cause, and will be 
discussed afterwards. 
How the disease may he spread .—If the gum exuding from an 
affected tree is examined it is found to contain innumerable 
reproductive bodies of the fungus, or conidia as they are techni¬ 
cally termed. And not only so, but these bodies are actively 
germinating, and so capable of growing on any suitable medium 
and reproducing a similar fungus to that from which they 
originated. Suppose a little portion of this gum containing these 
conidia at the stage when they aro ready to germinate is conveyed 
by any means to a citrus tree under favorable conditions for the 
growth of the fungus, then we may expect that the disease will 
appear. It is thus highly probable that the tools used for 
