34 
THE TROPICAL AGRICULTURIST. 
[July i, 1881. 
eiioe. But on different trees the disease establishes 
itself in a different (but for the same tree rarely 
Varying) force. There exists, therefore, a condition of 
the coffee tree, or more properly speaking, a condi- 
tion of the sap of the leaf cells which is peculiarly 
favourable to the development of the disease. In 
some trees this condition is continually present, and 
on thi se the disease can nearly always be found ; it 
is I here in a constant and chronic form. In the 
generality of trees, however, this condition occurs only 
twice a year, and it is during those two periods that 
the disease spreads itself from a few confined disease 
patches more or less all over the estate. 
In the majority of districts these two general attacks 
of the disease can be distinguished into a south-west 
and north-east monsoon attack, and they coincide 
closely, but generally precede by a little the natural, 
«o to speak autumnal fall of the coffee leaf which 
takes place to a more than usually appreciable extent 
twice a year. In many cases only one such fall will 
be acknowledged. 
These are periods, comparatively speaking, of a 
minimum of activity, of a minimum of alkalinity of 
the sap of the tree — periods when the trees are pre- 
paring their gathered stores of nutritious material 
for a new flush of leaves, when the cellular starch 
deposits are either changing or on the point of chang- 
ing into glucose, in order to enable its passage from 
one cell to the. other for the formation of cellulose 
at the apical or axillary buds. 
It is the period just before a maximum activity of 
the tree, during which the condition of the sap of 
the leaf cells appears to be most favourable to the 
penetration of I he germinated uredo-spore into the 
stomata of the coffee leaf and to its establishment in 
tbe intercellular tissue. The germinal tubes of this 
fungus share, no doubt, the apparent property of 
other absorptive vegetable forms, viz. that of an instinct- 
ive knowledge of the presence of congenial food. 
The condition of the sap of the coffee tree most con- 
genial to the establishment, of the fungus is, I take 
it, when the cellular starch deposits of the leaf are in 
a state of transition into glucose or sugar, which sub- 
stance, I am greatly of opinion, furnishes the chief foodof 
the fungus. And this transition, be it well borne in mind, 
can only take place in.the presence of a free acid. Thesap 
of weakly trees seems to be always in that condition. 
It remains only to be said that while I agree 
with others in considering the chief damage done 
by the disease due to the premature fall of leaf I 
would add to this, that I feel assured that the disease 
has a reactionary influence ; that it leaves behind in 
the tree, after a severe attack, a subtle poison, causing 
a subtle disposition in the tree to recreate the conditions 
favourable to its re-development, which interferes with 
and is antagonistic to the natural disposition of tbe tree to 
form stores of insoluble starch deposits. From these 
starch deposits fruit, in first the instance is formed. 
The fungus requires its food in a soluble form and after 
a series of attacks the trees appear to readily furnish 
it. Combine this with the premature fall of leaf, 
and short crops and the non-setting of blossom can 
be easily accounted for. 
EXPERIMENTS : 
WITH PROBABLE REMEDIES FOR THE DISEASE. 
My experiments were directed, 1st to ascertain whether 
the condition of the tree by assimilation of any chemical 
could be rendered less susceptible to the disease, 
and 2nd whether a practical method of topical 
application of some chemical or other, could not be 
devised that would act better than the sulphur and 
lime treatment and which would not result, as the 
latter seems to have done in the majority of cases, 
in leaving tbe trees, for some considerable time 
afterwards, in a more susceptible state as regards 
the disease than if they had never been treated. 
1st Set of Experiments. 
To eliminate, all chance of error and of mistaking 
cause and effect in these experiments, I decided 
to introduce the chemicals direct into the cambium 
of the stem by a system of lateral absorpi ion, which 
I called Inoculation. Doubt was expressed at the 
time as to whether absorption through the cambium 
could take place. This matter has finally been set 
at rest; for experiments made by me at Holbrook- 
estate with cinchona trees, showed that trees of 
about 150 lb. weight each, exclusive of roots, were 
capable of absorbing through the cambium in7£ days 
up to 60 lbs. of different chemical liquids, the non 
assimilated portion of the chemicals accumulating in 
the leaf cells until (only however in some cases) total 
collapse of the same ensued. 
These inocculation experiments have been detailed by 
me in a paper written at Doteloya and published 
in January and need not be republshed. My general 
conclusions are : — chlorides, nitrates, bieulphates, M'per- 
pho phates and all acids and sour organic manures are apt 
io increase the susceptibility of the tree to the disease. 
Sulphates, phosphates, or generally speaking neutral 
salts that can combine with another atomic weight of 
acid, all alkalies and antiseptic chemicals (other than 
chlorides and such as do not owe their anti-eptic charac- 
ter exclusively to their oxidising or deoxidising power) 
decrease the susceptibility of the tree to fall a victim 
to thedisease. Pre-eminently successfulamong the latter, 
I found carbonate of potash and carbolic acid. When 
absorbed into the system of the tree while the fungus 
was healthily established in the leaf tissue, either of 
these chemicals prevented the fructification of the 
pinspots, in some cases entirely ; in no case more than 
'22 per cent of them fruited, while on adjoining untreated 
coffee, under exactly similar conditions and during the 
same period, from 76 to 100 per cent of the observed pin- 
spots had fruited. 
Carbolic acid was the chemical I experimented with 
almost conclusively, after the preliminary experiments 
were over, as it had given me even more satisfactory 
results than tbe carbonate of potash. 
It was applied to the stem of the tree, mixed into a 
paste with fine soil and water in about 5 per cent 
strength, a slip of stout paper being tied round the tree 
in the shape of a cup to hold the paste. 
The chemical penetrated in sufficient strength iftto 
the cambium cells to cause their collapse for some dis- 
tance inwards, but the strength and causticity of the 
chemical decreased of course until weakened enough to 
effect entrance into the living cell without causing col- 
lapse. Traces, thereof (in a combined form of course) 
were bound to exert their influence on the leaf cells. 
One of the chief properties of carbolic acid is its cap- 
ability of arresting organic change or decay, this power 
being appreciably asserted in its most dilute form. 
The fungus, according to my conclusions, luxuriates 
in cellular tissue, contents of which are in a transient 
stage. Ihe faintest trace of carbolic acid will arrest thie, 
will stop for some time tbe conversion of the starch de- 
posits into sugar ; that is to say, will prevent the forma- 
tion of what constitutes, in my opinion, the chief food 
of the fungus — the result will, of course, be that the 
mycelium, if still young, will die without fructifica- 
tion for want of suitable food. And this has virtu- 
ally been the practical result of the above treatment. 
But the effect of the carbolic acid thus used is of 
an evanescent character, and I came, somewhat reluct- 
antly, to the conclusion that for this method to be of 
any practical value, considering the wide and universal 
prevalence of the different forms of the fungus, it 
would have to be supplemented by topical application 
calculated to destroy tbese forms. 
This led to recon^deration of the results of the 
second set of experiments, ending in my being able 
to combine the essential features of both. 
The inoculation process involved some danger to 
