Notes . 
i 7 2 
NOTE ON A NEW TREATMENT FOR SILVER-LEAF DISEASE IN 
FRUIT TREES. — The well-known phenomenon of ‘auto-digestion 5 shown by 
the fruit bodies of most species of Coprinus forms the theoretical basis for the 
treatment to be described. From the specific nature of enzyme action it is to 
be expected that a parasitic fungus has evolved tissues which are not destroyed 
by the enzymes used to dissolve the tissues of its host, and conversely that an enzyme 
which destroys the fungal mycelium will leave the host untouched. It seems probable, 
from the researches of Buller 1 and others, that a very powerful enzyme, capable 
of destroying the fungal mycelium, exists in the fruit bodies of Coprinus. The work 
which has been begun on Silver-leaf Disease is an attempt to use this enzyme 
as a curative agent. The disease is particularly well adapted to test the treatment 
because of the marked silvered appearance of the leaves of affected parts ; and also 
because the symptoms appear in the living branches before their invasion by the 
fungal mycelium, and so they can be fortified from attack before the tissues have 
become disorganized. This disease is supposed by most observers 2 to be due 
to Stereum purpureum , the mycelium of which is found in the dead branches of 
diseased trees, and which will reproduce the disease in healthy trees. The actual 
silvering of the leaves has been shown by Percival to be due to air cavities in certain 
of the walls of the epidermal cells, and may be due to the action of an enzyme 
secreted by the fungus ; but the fungal mycelium does not appear in the living tissues 
until a short time before death takes place. 
The treatment consists in hypodermic injections of a concentrated water extract 
from the ‘ diliquescing 5 fruit bodies of various species of Coprinus. Besides the 
injections, there is external application of the same extract, after the manner 
of a poultice, at the points of the dead wood where fruit bodies of Stereum make their 
appearance. The effect of the treatment is fairly well marked. A ‘poultice 5 causes 
the fungal fruit body to become greyish in colour and to peel off by degrees on to the 
soaked fabric of the ‘ poultice ’. One Victoria Plum tree, which has been treated with 
injections for two years, showed no silvering on the leaves of the upper parts of the 
branch in the autumn of 1912. When treatment was commenced, this branch, 
the last survivor of the five main branches of the tree, was badly affected throughout : 
it has now borne fruit in the two successive seasons, after a sterility of three years’ 
standing, and has produced remarkably vigorous new growth. The lower parts 
of the branch, near the infected dead wood, still showed slight silvering on the leaves 
last autumn. 
As the results so far seem encouraging, it is proposed to continue the experiments 
on a larger scale, to extend the treatment to other fungal diseases of plants and 
animals, and to investigate in the laboratory the precise nature of the enzyme 
in Coprinus and its effects. 
SARAH M. BAKER. 
University College, London. 
1 Buller : Researches on Fungi, London, 1909, chap. xix. 
2 Percival: Journ. Linn. Soc., Bot., 1902, vol. xxxv. Spencer Pickering: Report of the 
Woburn Experimental Fruit Farm. F. T. Brookes: Brit. Assoc. Reports, 1910, p. 776. 
